Tunnels used by the Mexican drug cartels

A Mexican army soldier using a flashlight shows reporters a tunnel connecting warehouses on either side of California’s border with Mexico in Tijuana. More than 75 such underground passages have been found along the border since 2008, concentrated largely in California and Arizona.

A news photographer walks inside a tunnel in the northern border city of Tijuana, Mexico in 2011 after a tunnel was discovered by U.S. authorities in San Diego’s Otay Mesa area.

An armed U.S. Border Patrol walks inside a huge underground rainwater drainage tunnel in Nogales, Ariz. The tunnel spans the border with Mexico and is often used by Mexican smugglers who break the welds on the grate and lift people and drugs up to the street.

A cross–border tunnel discovered south of San Diego is paved with textured concrete. Walls are the hard native clay–like soil. This passage leads 50 feet up from the deepest part of the tunnel to an opening in a warehouse about 1/2 mile north of the borderline. Two tons of marijuana were found on the Mexico side.

An Immigration Customs Enforcement special response member stops at an intersection in a cross–border tunnel discovered south of San Diego. Here at 50 feet below street level, this passage looks south about 3/10–mile from border with Mexico.

A Mexican federal police officer shines his flashlight on the ground of a tunnel that passes under the U.S.–Mexico border discovered in January 2006 in Tijuana. Federal law enforcement agents arrested Mexican drug lord Francisco Javier Arellano–Felix, a leader of a major violent gang responsible for digging these elaborate tunnels to smuggle drugs under the U.S. border.

A Mexican federal agent crawls through a hidden tunnel, presumably used to transport drugs from Mexico to the U.S., while being filmed by a television reporter in Tijuana in June 2004. The tunnel, which starts in an abandoned house in Tijuana, crosses under the U.S. border.

Mexican federal agents stand at the entrance to a hidden tunnel, presumably used to transport drugs from Mexico to the U.S., in Tijuana. The tunnel, which starts in an abandoned house in Tijuana, crosses under the U.S. border.

A Mexican federal police officer stands next to packages, believed to be marijuana, that had been removed from a sophisticated clandestine tunnel which passes under the U.S.-Mexico border in January 2006 in Tijuana. The tunnel, which is about 2,400 feet long and around 60 feet underground, is accessed through a large concrete block shaft in a warehouse south of the border.