Smugglers stacked the bundles of dope on a freight elevator that descended to an underground staging area, where electric carts whisked the marijuana down a tunnel into California.
The passageway linked a warehouse in Tijuana with another nondescript building in San Diego, and just like several other drug tunnels, its discovery this week yielded another jackpot seizure.
More than 32 tons of marijuana were seized in connection with the tunnel investigation, making it one of the largest drug seizures in U.S. history, and the latest in a series of enormous busts along the California-Mexico border.
Clever detective work and improved tunnel detection technology have made underground trafficking more difficult, authorities said. But the huge drug quantities heading across the border could also be explained by a surge in marijuana production in Mexico and, in particular, Baja California, where Mexico's Sinaloa drug cartel has been expanding its influence.
This week's bust comes two weeks after another tunnel investigation turned up 17 tons of pot. Last year, two other tunnel probes in the same area yielded 45 tons. In Baja California, Mexican authorities have made several record busts in the last two years, including the seizure of 134 tons of marijuana in Tijuana — the largest drug seizure in Mexican history — and the dismantling of a 300-acre pot farm south of Ensenada, also a record operation.
The recent surge in massive shipments could be a sign that Mexico's most powerful organized crime group, the Sinaloa drug cartel, has increased its control of Baja California, where the once powerful Arellano Felix drug cartel has been largely dismantled by killings and arrests.
The annihilation of the Arellano Felix cartel "was a big part of that," said William R. Sherman, acting special agent in charge of the Drug Enforcement Administration's office in San Diego. "Sinaloa has traditionally run a lot of marijuana through other ports, and I think now that they have more control of this port, that's certainly accounting for the large quantities we've been getting here in the last two years."
Investigators discovered the tunnel Tuesday inside a produce warehouse a few blocks north of the U.S.-Mexico border. The building had been under surveillance since May, and agents were able to obtain a search warrant after observing a tractor-trailer leave the warehouse and deliver a drug shipment to a warehouse in the City of Industry.
The 600-yard tunnel, equipped with an elevator, wooden flooring and a rail and cart system — was more impressive than at least six other sophisticated tunnels found in recent years, said Derek Benner, special agent in charge of Immigration and Customs Enforcement in San Diego.
On the Mexican side, the tunnel opening was concealed inside a building on the edge of the runway at Tijuana International Airport. A Mexican law enforcement official said the passageway appeared to follow a route directly under the runway where planes take off regularly.
Authorities found 4 tons of marijuana in the Tijuana warehouse; 17 in San Diego; and 11 in the City of Industry. Six people, including two truck drivers, were arrested and face drug conspiracy charges.
The seizures come at a time of increased marijuana production in Mexico. The acreage of marijuana under cultivation more than tripled from 2005 to 2009, from 13,800 to 43,200 acres, according to the most recent estimates compiled by the National Drug Intelligence Center.
In farm-growing regions of Baja California, farmers and laborers say the number of clandestine marijuana-growing operations has grown rapidly in recent years, straining water resources but providing more jobs. More than 100 laborers were needed to tend the fields at the giant marijuana farm south of Ensenada that was busted in July, Mexican authorities said
The large shipments encountered late in the year coincide with the harvest season for marijuana south of the border, officials said. The tunnel discovered this week, they said, had just recently become operational.
The considerable investment of time and money to construct such an elaborate tunnel showed that traffickers are desperate to get their product across an increasingly fortified border, said Laura Duffy, the U.S. attorney in San Diego. She dared traffickers to keep trying.
"If you build it, we will find it," Duffy said, "and when we find it, we will destroy it."