Twice before, the anti-drug agents had gotten a tip about a load of cocaine at the hulking industrial park on this dreary stretch of highway half an hour outside Guatemala City. Twice before, a U.S. official said, they had found nothing.
On their third visit, they found a firing squad.
Gunmen unleashed a furious barrage of bullets and at least one grenade, in some cases finishing the job point-blank. When the shooting stopped that day in April, five of the 10 Guatemalan agents lay dead and a sixth was wounded.
The fleeing killers, identified by authorities as members of the Mexican drug gang known as the Zetas, left behind a cargo truck packed with 700 pounds of cocaine. More stunning was the cache found in a brick warehouse: 11 M-60 machine guns, eight Claymore mines, a Chinese-made antitank rocket, more than 500 grenades, commando uniforms, bulletproof vests and thousands of rounds of ammunition.
"They were preparing for war," said the adjunct director of the National Civilian Police, Rember Larios.
As Mexican President Felipe Calderon presses a 2 1/2 -year-old offensive against narcotics traffickers in his country, the war has spilled south into Guatemala, where proximity, weak law enforcement and deeply rooted corruption provide fertile ground for Mexico's gangs, say officials and analysts in the region.
During the last year and a half, the Zetas have carved a bloody trail across Guatemala's northern and eastern provinces. More than 6,000 people were slain in Guatemala in 2008. Police say most of the killings were linked to the drug trade.
As the recent blood bath shows, the violence is now threatening the capital, deep in the interior.
Authorities say Mexican drug gangs, primarily the Zetas and rivals from the state of Sinaloa, are ramping up operations in Central America to evade increased marine patrols near Mexico as they relay drug shipments to the United States and Europe.
The gangs are also ferrying military-style weapons north into Mexico to fight Calderon's forces and opposing gangsters while also vying to take over street sales in Guatemala. Some of the weapons are left over from the wars that the United States helped fight in Central America -- including here in Guatemala, which is still recovering from its 36-year civil war.
"They're looking for new areas," said the U.S. official, who spoke on condition of anonymity because he wasn't authorized to comment on the matter. "They need a place where they can operate with impunity."
Since January 2008, Guatemalan police have arrested about 30 suspects who they said were working for the Zetas, the armed wing of the so-called Gulf cartel, based in northeastern Mexico.
The Zetas, formed in the 1990s from former Mexican special forces, have shaken Mexico in recent years through hundreds of well-planned killings and an expanding reach. The group has decapitated numerous rivals, dumping the heads in public places with menacing messages.
Authorities on edge
The spreading influence of Mexican traffickers has Guatemalan authorities on edge and is beginning to stir concern in Washington that powerful drug gangs could imperil fragile Guatemala and its weak neighbor, Honduras.
U.S. Rep. Eliot L. Engel (D-N.Y.) urged Secretary of State Hillary Rodham Clinton last month to steer more law-enforcement help to Guatemala, warning that it is even weaker than Mexico.
"It is essential that we view our efforts to combat drugs and violence in the Western Hemisphere in a more holistic way," said Engel, who chairs the Western Hemisphere subcommittee of the House Committee on Foreign Affairs.
Guatemalan police commanders say their 20,000 officers cannot match the firepower of the Mexican traffickers, who have made growing use in Mexico of military-type arms, such as 40-millimeter grenades and .50-caliber rifles capable of piercing armor.
Recent seizures in Guatemala have yielded similar weapons. "These are things we have seen only in photos of Iraq and the Gulf," said Larios, the police commander. "Not in Guatemala."
But devising a response is complicated by Guatemala's troubled past. The memory of the army's brutal conduct during the civil war means that it would be politically dicey for Guatemalan leaders to respond by mobilizing the military, as Calderon has done in Mexico.
Guatemala's army, which once ran the country, has been reined in since the 1996 peace accords, and many residents and human rights activists would be loath to lend it broad policing power. The military is summoned to back up civilian police and patrol distant reaches.
Foreign traffickers have long operated in Guatemala with the help of local smugglers. During the 1980s and early '90s, Colombian drug lords controlled the northbound pipeline for contraband, but Guatemalan and Mexican traffickers later took over.
Sinaloa-based kingpin Joaquin "El Chapo" Guzman, now Mexico's most-wanted drug suspect, was arrested in Guatemala in 1993. He was extradited to Mexico, but escaped from prison in 2001.
But Calderon's war on drug cartels in Mexico is creating a new wave. Pressured in Mexico, traffickers are shifting to Guatemala to store and repackage drugs, stockpile weapons and hide drug money, experts say.
U.S. officials say they believe more drugs are moving through Guatemala than before Calderon's crackdown. A recent analysis by Alberto Islas, a security specialist in Mexico, found foreign reserves in Guatemala's central bank growing robustly, despite economic troubles and falling transfers from Guatemalans abroad -- a sign that crime groups are parking money here.
The Zetas, who have reportedly gotten help from Guatemalan former special forces known as Kaibiles, have announced their presence with spectacular violence.
In November, a gun battle between trafficking gangs in the northwestern province of Huehuetenango, apparently over a disputed horse-race wager, left at least 17 people dead. Officials say the real toll may have been twice that, but many bodies apparently were hauled off before police arrived.
Several months earlier, in March, 11 people were killed when Zeta gunmen ambushed a suspected Guatemalan trafficker, Juan Jose "Juancho" Leon, and bodyguards at a swimming pool in the eastern province of Zacapa.
Guatemalan police say the high-profile arrests of a suspected top-ranking Zeta commander, Daniel Perez Rojas, and others show that the government of President Alvaro Colom is clamping down on drug trafficking.
They cite as evidence a jump in drug and weapons seizures since January 2008, when Colom took office. So far this year, authorities say, they have captured close to $2 billion worth of contraband and cash, roughly triple the figure for all of 2007, officials said.
"[Colom] has ordered a full-frontal attack against all organized crime, especially drug trafficking," said Roberto Solorzano, vice minister for public security in the Interior Ministry.
Nonetheless, unproven charges of drug ties have swirled around Colom, a left-leaning former businessman, since the 2007 presidential campaign. A Guatemala City attorney, Rodrigo Rosenberg, created a scandal when he charged last month that the president's inner circle was using the nation's rural-development bank, Banrural, to launder money. The videotaped allegations came out a day after Rosenberg was shot dead by unidentified assailants.
Many analysts say drug gangs, unchecked, could turn Guatemala into a full-fledged narco-state.
Despite efforts to clean up police forces, the criminal-justice system in Guatemala is rife with corruption and deeply mistrusted. Banking oversight is lax. And persistent poverty means a ready supply of potential helpers for the cash-rich drug gangs.
Already, traffickers operate freely in rural stretches nearest Mexico: building secret airstrips in the northern province of Peten to ferry shipments of cocaine, paying small-time farmers to grow poppy and moving contraband across the porous frontier into Mexico.
"If you can say Mexico is a failed state, Guatemala is worse," said Mario Merida, a security analyst and columnist in Guatemala City.
Fight for dominance
The battle among drug gangs to dominate smuggling and local sales has increased violence that was already at epidemic levels in Guatemala, officials and analysts say.
The rising drug violence has added to an overall sense of insecurity in the capital, where armed guards stand outside many businesses and residents say they are afraid to venture out at night.
In one suspected drug hit recently, gunmen in Guatemala City methodically stopped traffic and then opened fire on a woman in a car. Investigators found 79 spent shells at the death scene, including from an 8.6-millimeter rifle, often used by snipers.
Solorzano, the Interior Ministry official, said Guatemalan leaders are honing a new request for U.S. aid to train and equip police for fighting drug gangs. His country last year was allotted $10.6 million as a first installment of the so-called Merida Initiative, the lion's share of which is destined for Mexico: $1.4 billion over three years. Guatemala will receive a portion of $105 million approved for Central America this year.
While they wait for assistance, Guatemalan officials brace for more violence from Mexican traffickers.
The jitters are on display at the Guatemala City prison where Perez and the other suspected Zeta gunmen are held. Helmeted soldiers and special forces police in black berets guard the crumbling road leading to the main gate. Troops hide in the bushes on the steep hillside above it. Armored military vehicles, with .50-caliber machine guns front and back, make constant passes.
But perhaps the authorities' most eloquent sign of worry about a mass breakout sits outside the entrance. It is a mobile antiaircraft gun, placed there in case Mexican gangsters swoop down from the sky.