A 21/2-month-long investigation of the underground passageway, discovered by American drug agents in late February, has revealed a sophisticated operation that officials believe was active for at least a decade, far longer than they originally thought. U.S. Drug Enforcement Administration officials say the tunnel was one of the most profitable smuggling avenues used by the notorious Arellano Felix drug cartel to transport drugs to the U.S. and bring weapons and money back into Mexico.
"What's scary is that here we have so much security along the border, yet they could have moved so much product without being caught," said Donald Thornhill Jr., a spokesman for the DEA's San Diego office. "It's humbling when you just consider the length of time we think this thing was being used."
This is not the first drug tunnel found burrowed under the U.S.-Mexico border, but it is one of the most elaborate. The examination of the secret corridor, which has been cemented shut, provided agents with clues to an extensive construction process that may have taken as long as two years.
Digging through the hard soil, pocked with rocks, would have been a backbreaking endeavor that required the use of jackhammers, drills and picks, at a pace of probably a foot a day, DEA officials said.
When it was completed, however, the corridor provided a near-foolproof way to transport contraband undetected. In fact, the smugglers using the corridor were so confident in its security that when DEA agents discovered the passageway on Feb. 27, acting on a tip from a previous drug seizure, they found 300 pounds of marijuana inside.
The tunnel began under a fireplace in the ranch house outside Tecate, where a hydraulic lift was used to move a steel grate in the floor, revealing a passageway below.
Investigators believe a small room below the fireplace was used as a staging area to sort and package drugs. From there, the 875-foot passageway wended its way through the earth to a barn-style house in a rural area of eastern San Diego County known as Tierra del Sol. At the end of the tunnel, a ladder led up to a floor safe hidden behind a staircase in the house. The safe and the staircase could be swung open with levers.
The designers of the operation had to know about engineering, welding and electrical wiring, officials said.
"They did a real bang-up job," Thornhill said.
The 4-by-4-foot tunnel was reinforced with planks of wood that covered the entire length of the passageway. Railroad tracks were laid along the floor to transport a battery-operated cart, which pulled two flatbed cars. A ventilation pipe ran the length of the passageway, and lightbulbs were strung from the ceiling every 50 feet.
Using the rail carts, a shipment of drugs could reach the other side of the border in minutes.
U.S. officials believe the tunnel may have existed in a rough form as long as 20 years ago, as a small "rabbit hole" used by traffickers to get drugs north without detection.
A more formal tunnel was probably constructed about 10 or 12 years ago, when the homes that covered the openings on either side were being built, Mexican and U.S. officials said.
But finding the passageways is not easy, Thornhill said.
"We can't just go onto private property and look for tunnels," he said. "We have to have a reason."