Authorities seized 8 1/2 tons of marijuana and 327 pounds of cocaine in connection with the tunnel's discovery, according to court records. Three men who authorities say worked as drivers were charged Thursday with possession of marijuana and cocaine with intent to distribute. U.S. Attorney Laura Duffy said they face prison sentences between 10 years and life if convicted.
The tunnel, which zigzags the length of nearly six football fields, links warehouses in Tijuana and San Diego's Otay Mesa industrial area. The area is filled with nondescript warehouses, making it easier to conceal trucks being loaded with drugs.
The tunnel was shut down Wednesday night, before any drugs made it through undetected, authorities said. Federal agents had the San Diego warehouse under surveillance after being tipped off by an informant who told them that operators bought drills and other construction equipment in August and September.
As U.S. border security has heightened on land, Mexican drug cartels have turned to ultralight aircraft, small fishing boats and tunnels. More than 75 underground passages have been discovered along the border since 2008, designed largely to smuggle marijuana.
The tunnels are concentrated along the border in California and Arizona. San Diego is popular because its clay-like soil is easy to dig. In Nogales, Ariz., smugglers tap into vast underground drainage canals.
The tunnel is the eighth major passage discovered in San Diego since 2006, a period during which Mexico's Sinaloa cartel has solidified its hold on the prized smuggling corridor. Authorities said Wednesday's tunnel was the first in the San Diego area that was found to be used for cocaine.
The passage was about 35 feet underground, 4 feet high and 3 feet wide, said Derek Benner, U.S. Immigration and Customs Enforcement's head of Homeland Security Investigations in San Diego. Authorities said the zigzag route suggests that excavators veered off course several times.
Some of the largest tunnels have been discovered after central Mexico's marijuana harvest in October, which presents drug cartels with a challenge of how to quickly get their product to consumers.
In November 2011, authorities found a 600-yard tunnel that resulted in seizures of 32 tons of marijuana on both sides of the border, with 26 tons found on the U.S. side, accounting for one of the largest pot busts in U.S. history. The tunnel was equipped with electric rail cars, lighting and ventilation. Wooden planks lined the floor.
On Thanksgiving Day 2010, authorities found a roughly 700-yard passage equipped with rail tracks that extended from the kitchen of a Tijuana home to two San Diego warehouses, netting about 22 tons of marijuana on both sides of the border.
Seizures linked to the tunnel include a haul of 3 tons of marijuana in a truck that was stopped by Chula Vista police on Saturday for a traffic violation and 5 1/2 tons of marijuana inside the tunnel, a nearby warehouse and a truck Wednesday, according to prosecutors. The cocaine was found in six suitcases inside a van seen leaving the warehouse Wednesday.
