The elaborate set-up was a four-foot by four-foot corridor with electric lights, fresh air vents, steel rails and a push car that moved an estimated billions of dollars worth of drugs from Tecate, Mexico to a sparsely furnished house near the mountain town of Tierra del Sol, Calif.
"The sole purpose of the tunnel was to smuggle narcotics — cocaine, marijuana," said Errol Chavez of the Drug Enforcement Agency.
On the American side, the opening was beneath a floor safe where agents recovered 500 pounds of freshly harvested marijuana. On the Mexican side, where two men were arrested, the tunnel entrance was concealed behind a fireplace.
And it was all believed to be under the control of a Tijuana drug cartel — a cartel that rented the corridor out to other drug smugglers who sometimes paid dearly, reports CBS News Correspondent Jerry Bowen.
"We have information from other investigations that they have actually intimidated, killed traffickers who have not paid the toll," said Chavez.
Investigators say the tunnel has been in use for at least three years and is the largest found since 1993, when a quarter mile long tunnel was found running from a warehouse in Tijuana to one under construction on the U.S. side. But it's not the last, say authorities, who are convinced there are more tunnels out there, they just don't know where.