The tomatoes, peppers and cucumbers arrive year-round by the ton, with peel-off stickers proclaiming "Product of Mexico."
Farm exports to the U.S. from Mexico have tripled to $7.6 billion in the last decade, enriching agribusinesses, distributors and retailers.
American consumers get all the salsa, squash and melons they can eat at affordable prices. And top U.S. brands — Wal-Mart, Whole Foods, Subway and Safeway, among many others — profit from produce they have come to depend on.
These corporations say their Mexican suppliers have committed to decent treatment and living conditions for workers.
But a Los Angeles Times investigation found that for thousands of farm laborers south of the border, the export boom is a story of exploitation and extreme hardship.
The Times found:
Many farm laborers are essentially trapped for months at a time in rat-infested camps, often without beds and sometimes without functioning toilets or a reliable water supply.
Some camp bosses illegally withhold wages to prevent workers from leaving during peak harvest periods.
Laborers often go deep in debt paying inflated prices for necessities at company stores. Some are reduced to scavenging for food when their credit is cut off. It's common for laborers to head home penniless at the end of a harvest.
Those who seek to escape their debts and miserable living conditions have to contend with guards, barbed-wire fences and sometimes threats of violence from camp supervisors.
Major U.S. companies have done little to enforce social responsibility guidelines that call for basic worker protections such as clean housing and fair pay practices.
The farm laborers are mostly indigenous people from Mexico's poorest regions. Bused hundreds of miles to vast agricultural complexes, they work six days a week for the equivalent of $8 to $12 a day.
The squalid camps where they live, sometimes sleeping on scraps of cardboard on concrete floors, are operated by the same agribusinesses that employ advanced growing techniques and sanitary measures in their fields and greenhouses.
The contrast between the treatment of produce and of people is stark.
In immaculate greenhouses, laborers are ordered to use hand sanitizers and schooled in how to pamper the produce. They're required to keep their fingernails carefully trimmed so the fruit will arrive unblemished in U.S. supermarkets.
"They want us to take such great care of the tomatoes, but they don't take care of us," said Japolina Jaimez, a field hand at Rene Produce, a grower of tomatoes, peppers and cucumbers in the northwestern state of Sinaloa. "Look at how we live."
He pointed to co-workers and their children, bathing in an irrigation canal because the camp's showers had no water that day.
At the mega-farms that supply major American retailers, child labor has been largely eradicated. But on many small and mid-sized farms, children still work the fields, picking chiles, tomatillos and other produce, some of which makes its way to the U.S. through middlemen. About 100,000 children younger than 14 pick crops for pay, according to the Mexican government's most recent estimate.
During The Times' 18-month investigation, a reporter and a photographer traveled across nine Mexican states, observing conditions at farm labor camps and interviewing hundreds of workers.
At half the 30 camps they visited, laborers were in effect prevented from leaving because their wages were being withheld or they owed money to the company store, or both.
Some of the worst camps were linked to companies that have been lauded by government and industry groups. Mexico's President Enrique Peña Nieto presented at least two of them with "exporter of the year" honors.
The Times traced produce from fields to U.S. supermarket shelves using Mexican government export data, food safety reports from independent auditors, California pesticide surveys that identify the origin of imported produce, and numerous interviews with company officials and industry experts.
The practice of withholding wages, although barred by Mexican law, persists, especially for workers recruited from indigenous areas, according to government officials and a 2010 report by the federal Secretariat of Social Development. These laborers typically work under three-month contracts and are not paid until the end. The law says they must be paid weekly.
The Times visited five big export farms where wages were being withheld. Each employed hundreds of workers.
Wal-Mart, the world's largest retailer, bought produce directly or through middlemen from at least three of those farms, The Times found.
Bosses at one of Mexico's biggest growers, Bioparques de Occidente in the state of Jalisco, not only withheld wages but kept hundreds of workers in a labor camp against their will and beat some who tried to escape, according to laborers and Mexican authorities.
Asked about its ties to Bioparques and other farms where workers were exploited, Wal-Mart released this statement:
"We care about the men and women in our supply chain, and recognize that challenges remain in this industry. We know the world is a big place. While our standards and audits make things better around the world, we won't catch every instance when people do things that are wrong."
At Rene Produce in Sinaloa, The Times saw hungry laborers hunting for scraps because they could not afford to buy food at the company store.
The grower, which exported $55 million in tomatoes in 2014, supplies supermarkets across the U.S., including Whole Foods, which recently took out full-page newspaper ads promoting its commitment to social responsibility.
Asked for comment, Whole Foods said it did not expect to buy any more produce "directly" from Rene, which it described as a minor supplier.
"We take the findings you shared VERY seriously, especially since Rene has signed our social accountability agreement," Edmund LaMacchia, a global vice president of procurement for Whole Foods, said in a statement.
Rene Produce was named one of Mexico's exporters of the year in September.
Jose Humberto Garcia, the company's chief operating officer, said Rene had consulted with outside experts about ways to enhance worker welfare. "We have tried in recent years to improve the lives of our workers," he said. "There's still room for improvement. There's always room for improvement."
Executives at Triple H in Sinaloa, another exporter of the year and a distributor for major supermarkets across the U.S., said they were surprised to hear about abusive labor practices at farms including one of their suppliers, Agricola San Emilio.
"It completely violates our principles," said Heriberto Vlaminck, Triple H's general director.
His son Heriberto Vlaminck Jr., the company's commercial director, added: "I find it incredible that people work under these conditions."
In northern Mexico, agro-industrial complexes stretch for miles across coastal plains and inland valleys, their white rows of tent-like hothouses so vast they can be seen from space.
Half the tomatoes consumed in the U.S. come from Mexico, mostly from the area around Culiacan, the capital of Sinaloa. Many farms use growing techniques from Europe. Walls of tomato vines grow 10 feet tall and are picked by laborers on stilts.
Agricola San Emilio raises crops on 370 acres of open fields and greenhouses 20 miles west of Culiacan. In a tin-roofed packinghouse, tomatoes, bell peppers and cucumbers are boxed for the journey north to distributors for Wal-Mart, Olive Garden, Safeway, Subway and other retailers.
In 2014, the company exported more than 80 million pounds of tomatoes alone, according to government data.
Every winter, 1,000 workers arrive at San Emilio by bus with backpacks and blankets, hoping to make enough money to support family members back home. Some simply want to stay fed.
Behind the packing facility lies the company's main labor camp, a cluster of low-slung buildings made of cinder block or corrugated metal where about 500 laborers live.
The shed-like structures are crudely partitioned into tiny rooms that house four to six people each. The floors are concrete. There are no beds or other furniture, nor any windows.
The workers' day begins at 3 a.m. when a freight train known as "The Beast" rumbles past the dusty camp, rousting the inhabitants. They get coffee, a biscuit and a short stack of tortillas before heading to the fields.
When Times journalists visited the camp in March, Juan Ramirez, a 22-year-old with a toddler back home in Veracruz, had been working at San Emilio for six weeks and had yet to be paid.
He and other laborers spent their days picking, packing and pruning, or scouring the plants for weevils. They lined up for their daily meals: a bowl of lentil soup for lunch, a bowl of lentil soup for dinner.
Ramirez, wearing a stained white T-shirt, chatted with two young men who were recent arrivals. They complained of hunger and constant headaches. Ramirez knew the feeling. He had lost 20 pounds since starting work at the farm.
"We arrive here fat, and leave skinny," he said.
Ramirez and several hundred others recruited by the same labor contractor earned $8 a day and were owed as much as $300 each. They said they wouldn't be paid until the end of their three-month contracts. That would be in six more weeks.
Workers said they had been promised $8 in pocket money every two weeks but received it only sporadically.
If they left now, they would forfeit the wages they'd earned. The barbed-wire fence that ringed the camp was an added deterrent. Farm owners say the barriers are meant to keep out thieves and drug dealers. They also serve another purpose: to discourage laborers from leaving before the crop has been picked and they've paid their debts to the company store.
Even if the workers at San Emilio jumped the fence, as some had, they wouldn't be able to afford a ride to Culiacan, let alone $100 for the bus ticket home.
Juan Hernandez, a father of five from Veracruz, was worried about his wife, who had been injured in an accident back home. "I want to go," he said. "But if I leave, I lose everything."
Hernandez slept atop packing crates padded with cardboard. A suitcase served as his dinner table.
In another building, Jacinto Santiago hung a scrap of cardboard in the open doorway of his room, which he shared with his son, daughter and son-in-law.
Santiago said that in some ways, he had been better off back home in the central state of San Luis Potosi. There, he had a thatched-roof house with windows and a hen that laid eggs.
Santiago, like the other laborers, said he was promised that he would be able to send money home. His family was still waiting, because he hadn't been paid. "My family isn't the only one that suffers. Anyone who has a family at home suffers," he said.
Efrain Hernandez, 18, said recruiters told him his earnings would be held back so he wouldn't get robbed: "They said it was for my own good."
Outside one of the buildings, a group of men gathered under a dim light. It was nearing the 9 p.m. curfew, when the camp's heavy metal gate rolls shut and workers retreat to their rooms.
Their voices echoed across the compound as they swapped stories about conditions in various camps. There are at least 200 across Mexico, 150 in Sinaloa alone.
Pedro Hernandez, 51, complained that unlike some other camps, San Emilio didn't offer beds or blankets. Then again, there were fewer rats, he said.
The conversation attracted a camp supervisor, who was surprised to see a reporter and photographer.
"When the people from Wal-Mart come," she said, "they let us know in advance."
She walked the journalists to the exit. The pickers went back to their rooms. The gate rolled shut.
The road to labor camps like San Emilio begins deep in the indigenous regions of central and southern Mexico, where advertising jingles play endlessly on the radio, echoing from storefront speakers.
"Attention. Attention. We are looking for 400 peasants to pick tomatoes."
"You'll earn 100 pesos per day, three free meals per day and overtime."
"Vamonos a trabajar!" — Let's go work!
On a warm January morning this year, dozens of indigenous people looking for work descended from mud-hut villages in the steep mountains of the Huasteca region. Nahuatl men wore holstered machetes. Women cradled children in their arms. Young men shouldered backpacks stuffed with the clothes they would wear for the next few months.
The laborers approached a knot of recruiters gathered outside a gas station in the town of Huejutla de Reyes, about 130 miles north of Mexico City.
Among those offering jobs at distant farms was Luis Garcia, 37. Garcia, a stocky Nahuatl Indian with silver-rimmed teeth, had risen from child picker to field boss to labor contractor for Agricola San Emilio. He lived just outside town, in a hilltop house behind tall gates, and was known to locals as "Don Luis."
"We all owe our livelihoods to the farmworkers," he said. "We have to treat them well, or the gringos don't get their tomatoes."
Labor contractors are key players in the agricultural economy, the link between export farms in the north and peasants in Huasteca and other impoverished regions. An estimated 150,000 make the pilgrimage every harvest season.
The contractors, working for agribusinesses, transport laborers to and from the farms. Often, they also oversee the camps and distribute workers' pay.
Many contractors abuse their power, according to indigenous leaders and federal inspectors. They lie about wages and living conditions at the camps. Under pressure from growers, they sometimes refuse to bring laborers home, even at the end of their contracts, if there are still vegetables to be picked.
Earlier this year, 25 farmworkers walked 20 miles across a Baja California desert after a contractor left them on the roadside, short of their destination.
At the gas station in Huejutla de Reyes, villagers listened warily to the recruiters' pitches. One was said to be representing a contractor wanted on human trafficking charges. Another worked for a contractor notorious for wage theft and other abuses.
Garcia had his own brush with controversy several years ago, when dozens of pickers accused him of holding them captive and abusing them at an onion farm in Chihuahua.
"They said I beat people. Lies, all lies," Garcia said, bristling. "I wouldn't be here today talking to you if it was true, would I?"
He depicted himself as a reformer who wanted to establish a trade association to set standards and drive out unscrupulous
But he saw no need to do more for workers. "The more protected they are, the less they work," he said.
As he spoke, recruiters tried to outbid one another for laborers, boosting their offers of spending money for the two-day bus trip to Sinaloa.
Garcia won the day's competition. With his smooth baritone, he persuaded about 40 people to get on his bus.
Garcia read their contract aloud to the workers, including the provision that they wouldn't be paid until the end of their three-month term. He later acknowledged that federal law requires weekly payments but said that there were other issues to consider.
"Paying them every week is a problem because it causes lots of issues with drinking and drugging and violence," Garcia said. "Huasteca people are fighters when they're drunk."
Proud of his success in a cutthroat business, Garcia portrayed himself as the product of a farm labor system in which the real bosses were U.S. companies.
"The gringos are the ones that put up the money and make the rules," he said.
The U.S. companies linked to Agricola San Emilio through distributors have plenty of rules, but they serve mainly to protect American consumers, not Mexican field hands.
Strict U.S. laws govern the safety and cleanliness of imported fruits and vegetables. To meet those standards, retailers and distributors send inspectors to Mexico to examine fields, greenhouses and packing plants.
The companies say they are also committed to workers' well-being and cite their ethical sourcing guidelines. Retailers increasingly promote the idea that the food they sell not only is tasty and healthful but was produced without exploiting workers.
But at many big corporations, enforcement of those standards is weak to nonexistent, and often relies on Mexican growers to monitor themselves, The Times found.
In some low-wage countries, U.S. retailers rely on independent auditors to verify that suppliers in apparel, footwear and other industries comply with social responsibility guidelines.
For the most part, that has not happened with Mexican farm labor. American companies have not made oversight a priority because they haven't been pressured to do so. There is little public awareness of harsh conditions at labor camps. Many farms are in areas torn by drug violence, which has discouraged media coverage and visits by human rights groups and academic researchers.
Asked to comment on conditions at Agricola San Emilio, Subway said in a statement: "We will use this opportunity to reinforce our Code of Conduct with our suppliers." The code says suppliers must ensure that workers "are fairly compensated and are not exploited in any way."
Safeway said: "We take any and all claims regarding worker conditions seriously and are looking into each of the points you raise."
In its vendor code of conduct, Safeway says that suppliers must offer a "safe and healthy work environment" and that it "will not tolerate any departure from its standards." Vendors are expected to "self-monitor their compliance," the code says.
Wal-Mart sought to distance itself from Agricola San Emilio, saying in a statement: "Our records show that we do not currently take from this facility."
Asked if it had received produce from the farm in the past, Wal-Mart repeated its statement.
Executives at Agricola San Emilio and two firms that have distributed its produce — Triple H of Culiacan and Andrew & Williamson of San Diego — said Wal-Mart received shipments from the Mexican farm this year.
John Farrington, chief operating officer at Andrew & Williamson, said that his company shipped San Emilio tomatoes to the retailer and that inspectors from Wal-Mart had been to the farm.
Mari Cabanillas, an assistant camp supervisor at Agricola San Emilio, said Wal-Mart inspectors visited regularly, recommending cleanups and fresh coats of paint.
"They try and improve conditions here," she said. "They're very strict."
As for Agricola San Emilio's pay practices, Daniel Beltran, the firm's director and legal counsel, said workers from the Huasteca region whose wages were withheld until the end of their three-month contracts had agreed to that arrangement. He said they could opt to be paid weekly, as others were.
A dozen workers, however, said in interviews that they had no choice in how they were paid.
Withholding workers' pay is illegal even if they agree to it, according to Mexico's federal labor law, a senior federal labor official and two labor lawyers.
In regard to living conditions, Beltran said the company stopped providing beds because workers dismantled them for firewood. The laborers are from regions where it's common for people to sleep on the floor, he said.
He took issue with workers' claims that they were underfed. "Some people, even if you give them chicken or beef every day, they'll still want a different menu," he said, adding that workers could supplement company rations by purchasing food from vendors.
SunFed, an Arizona firm that has distributed produce from Agricola San Emilio, said its representatives had inspected the fields and packinghouse at the farm but not the labor camp.
"The Mexican government would be the first line of protection for Mexican workers," said Dan Mandel, president of SunFed, a distributor for supermarkets across the U.S.
Enforcement of Mexican labor laws in Sinaloa is feeble. One state official insisted, incorrectly, that withholding wages until the end of a contract was legal.
Federal labor inspectors are clear on the law but said they were largely powerless to crack down on deep-pocketed growers, who can stymie enforcement with endless appeals.
"They just laugh at us," said Armando Guzman, a senior official with Mexico's federal Secretariat of Labor and Social Welfare. "They mock authority and mock the letter of the law."
Agricola San Emilio is no outlier. Harsh conditions persist in many camps.
At Agricola Rita Rosario, a cucumber exporter near Culiacan in Sinaloa, workers said they hadn't been paid in weeks. Some were pawning their belongings to pay for diapers and food when Times journalists visited a year ago. Laborers said company managers had threatened to dump their possessions in the street if they persisted in demanding their wages.
"We have nowhere to go. We're trapped," said a 43-year-old man, looking around nervously.
Rita Rosario, under new management, started paying workers their back wages this year before suspending operations, according to a U.S. distributor who did business with the farm.
Workers at Agricola Santa Teresa, an export farm nearby, were doing odd jobs outside the camp on Sundays to earn spending money because their wages had been withheld.
The tomato grower supplies U.S. distributors whose customers include the Albertsons supermarket chain and the Los Angeles Unified School District.
Told that workers hadn't been paid, Enrique Lopez, director of Santa Teresa, said it wasn't the company's fault. Santa Teresa pays them by electronic bank deposit every week, he said.
Lopez said he suspected that the laborers handed over their ATM cards to the contractor who recruited them, a practice he said was customary for workers from indigenous regions.
"That is the agreement they have," Lopez said. "We can't control that situation."
An LAUSD spokeswoman, Ellen Morgan, said the district requires suppliers to inspect farms from which they buy produce, primarily to ensure food safety. She said the district was formulating a new procurement policy that would probably address labor conditions too.
Albertsons declined to comment.
At Agricola El Porvenir, also near Culiacan, workers were required to disinfect their hands before picking cucumbers. Yet they were given just two pieces of toilet paper to use at the outhouses.
At Campo San Jose, where many of them lived, workers said rats and feral cats had the run of the cramped living quarters and feasted on their leftovers.
Laborers and their families bathed in an irrigation canal because the water had run out in the showers. In March, a snake was sighted in the canal, sparking a panic.
Carmen Garcia stepped out of the fetid waterway after washing her 1-year-old grandson. His skin was covered with boils that she blamed on insect bites.
"He itches constantly," Garcia said. "I want to get a blood test, but I can't get to a doctor."
Agricola El Porvenir's legal counsel, Eric Gerardo, said the company rents Campo San Jose from another agribusiness to handle the overflow when its own camps fill up. Efforts to reach the owner of the other business were unsuccessful.
"We don't invest in it because it's not ours," Gerardo said.
Twenty miles away, at Campo Isabelitas, operated by the agribusiness Nueva Yamal, families used buckets in their room to relieve themselves because, they said, the toilets were filthy and lacked water.
Men defecated in a cornfield. Workers could be seen bathing in an irrigation canal; they said the camp's showers were out of water.
Charles Ciruli, a co-owner of Arizona-based Ciruli Bros., which distributes Nueva Yamal tomatoes, visited the camp after being told about conditions there by The Times.
Through an attorney, he said that the men's bathrooms "did not meet Ciruli's standards" and that repairs had been made to "reinstate running water." The attorney, Stanley G. Feldman, said in a letter that the women's showers and toilets were "fully functioning," with a paid attendant.
Asked why workers were washing in the irrigation canal, Feldman wrote: "Ciruli cannot explain this with certainty, but it was told that it may be a cultural practice among some workers."
He added: "Ciruli will consult with the on-farm social worker and doctor to determine if a worker education campaign may be appropriate in this case."
In June 2013, Bioparques found itself under rare government scrutiny. Three workers at one of the tomato grower's labor camps escaped and complained to authorities about the wretched conditions.
Police, soldiers and labor inspectors raided the camp and found 275 people trapped inside. Dozens were malnourished, including 24 children, authorities said.
People were desperate, but at least the camp had showers and stoves, said laborer Gerardo Gonzalez Hernandez.
"To tell you the truth, Bioparques was a little better than other labor camps I've been to," Gonzalez, 18, said in an interview at his home in the mountains north of Mexico City.
"That's why I didn't complain. I've seen a lot worse."
Cecilia Sanchez, a researcher in The Times' Mexico City bureau, contributed to this report.
Coming next: A raid exposes brutal conditions at Bioparques, one of Mexico's biggest tomato exporters, which was a Wal-Mart supplier. But the effort to hold the grower accountable is looking more like a tale of impunity.
About this series: Los Angeles Times reporter Richard Marosi and photojournalist Don Bartletti traveled across nine Mexican states, observing conditions and interviewing workers at some of the mega-farms that have powered the country's agricultural export boom.