SAN DIEGO -- A drug-smuggling tunnel believed to be the longest one ever has been discovered underneath the U.S. and Mexico.
Feds announced the discovery Wednesday, saying the narrow passageway runs for nearly a half-mile between Otay Mesa and Tijuana, and is outfitted with lights, a ventilation system and an elevator.
An observant Border Patrol agent's suspicions led to a roughly eight-month investigation that ended last week with six arrests and the discovery of the tunnel.
The subterranean passageway connects a run-down home in Baja California to a fenced-off lot filled with wooden pallets in the far southern reaches of San Diego, according to KSWB.
The north end of the tunnel was hidden by a "jumbo-sized'' commercial trash bin that doubled as a container for narcotics spirited into the United States, U.S. Attorney Laura Duffy told reporters during a midday briefing.
A small opening hidden by gravel spread over the lid -- "literally a hole in the ground'' -- led to the roughly 10-foot-deep, three-foot-diameter zigzagging underground channel, in which agents found 68 packages of marijuana weighing a combined 1,600 pounds, Duffy said.
Three people were arrested at the storage property and another three were taken into custody at a parking lot on Imperial Avenue, near 30th Street in San Diego, where traffickers had taken the garbage bin and partially unloaded its cargo of drugs into a truck.
In the vehicle, agents found about 11,000 pounds of cannabis and 2,242 pounds of cocaine. The cocaine seizure is believed to be the largest ever made in California in connection with a smuggling tunnel, according to Duffy. In the commercial trash container was another 1,430 pounds of marijuana, she said.
Investigators said the thwarted delivery was the first real smuggling attempt after a series of "dry runs'' observed by agents who had the pallet-filled lot under surveillance for months, the U.S. attorney said.
The southern end of the passageway emerges into a commercial- grade elevator concealed in a closet in a Tijuana "flophouse'' with mattresses strewn about inside, Duffy said during the news conference at the Otay Mesa lot, where a sign reading "Otay Pallets -- We Buy Pallets'' was posted on the perimeter fence.
The discovery came six months after U.S. and Mexican investigators ferreted out a well-appointed tunnel stretching almost as far underneath the international line between warehouses in the same two border communities.
Law enforcement agents raided that roughly 800-yard-long passageway -- which was outfitted with ventilation, electric lighting and rails for ferrying contraband -- on the night of Oct. 21, hours after it went into use for the first time, authorities said at the time.