By SETH HETTENA
Associated Press Writer
SAN DIEGO- Those associated with the longest and one of the most sophisticated tunnels ever discovered along the U.S.-Mexico border may be in grave danger, U.S. officials said Friday.U.S. Immigration and Customs Enforcement said it had received intelligence that a Mexican drug cartel behind the tunnel had threatened the lives of people who had used it or were involved the passageway's design or construction.
The agency appealed to those whose lives were at risk to seek out U.S. officials at Mexican border crossings and pledged to do everything possible to protect them.
More than 2 tons of marijuana were found inside the tunnel discovered this week, which ran about 2,400 feet from a warehouse near the airport in Tijuana, Mexico, to a warehouse in San Diego's Otay Mesa industrial district.
As deep as 90 feet below the surface, authorities found a floor lined with cement, lights that ran down one of the hard soil walls, a groundwater pump and pipes that circulated fresh air, he said. An adult could stand in the 5-foot-high shaft.
"There is no doubt that an organization like this will take whatever steps necessary to protect their interests, including taking human lives," said Michael Unzueta, special agent in charge of the agency's investigations in San Diego.
It was unclear how long the tunnel had been in operation.
Copyright 2013 Associated Press. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.