Cops discover 2,600ft 'longest ever drug trafficking' tunnel crammed with cocaine and 7 tons of marijuana in U.S.-Mexico border

Cops have discovered a 2,600-foot-long drug trafficking tunnel beneath the U.S.-Mexico border, packed with seven tons of marijuana and a ton of cocaine.Six people have been arrested following the unearthing of the underground passageway, which could be the longest cross-border tunnel in history. See photos after the cut.

They remain in custody on various drug -trafficking conspiracy charges. 

The discovery comes as the world marks 420 Day, or 'Weed Day', when cannabis users gather in parks, homes and other venues to smoke the drug.

Federal agents in San Diego, California, moved this week to shut down the tunnel, the 13th underground passageway discovered along the state's border with Mexico since 2006. 

The half-a-mile-long tunnel, one of the narrowest found in the region, yielded an unprecedented cache of drugs, officials said.

"This is the largest cocaine seizure ever associated with a tunnel," said Laura Duffy, U.S. Attorney for the Southern District of California.

The northern end of the tunnel, like most of the others, emerges in a narrow industrial expanse between the Otay Mesa port of entry and the California Highway Patrol's border facility.

The area, known for its heavy clay soil, is primarily traversed by trucks hauling tons of legitimate cargo between the two countries every day.

The latest tunnel, excavated 46 feet beneath the surface, ran from the bottom of an elevator shaft built into a house in Tijuana to a hole in the ground on the U.S. side enclosed within a fenced-in lot set up as a pallet business.

The hole was concealed under a trailer-sized trash dumpster that smugglers used to move the drugs off the lot, federal officials said.

"They put the drugs in the dumpster and then hauled the dumpster to another location to unload it," Duffy said.

Agents followed a truck that carted the dumpster to a central San Diego spot about 25 miles north of the border and watched as the cargo was loaded onto a box truck, which drove away.

San Diego County sheriff's deputies who stopped the truck seized 2,242 pounds of cocaine and 11,030 pounds of marijuana, and arrested three men, Duffy said.

Federal agents searching the pallet lot and the tunnel recovered an additional 3,000-plus pounds of marijuana and arrested three more suspects, she said.

The suspects were all jailed on drug-trafficking conspiracy charges.