Drug tunnels of Mexico

The US entryway of a cross border tunnel located in a storage room inside a business, with 55 gallon drums filled with dirt and soil from excavation sitting on the side are pictured in this undated handout photo taken by the DEA in San Luis, Arizona....more

A military truck is parked outside a recycling plant where soldiers found a tunnel under construction at the Otay Mesa industrial park in Tijuana July 12, 2012. The Mexican Army located the tunnel in this border, which would be used for smuggling...more

The US entryway of a cross border tunnel is pictured in this undated handout photo taken by the DEA in San Luis, Arizona. REUTERS/DEA/Handout

Soldiers inspect the entrance of a cross border tunnel at a warehouse in Tijuana July 12, 2012. REUTERS/Jorge Duenes

The interior of a cross border tunnel is pictured in this undated handout photo taken by the DEA in San Luis, Arizona. REUTERS/DEA/Handout

Thirty-nine pounds of methamphetamines that were smuggled through a cross border tunnel is pictured in this undated handout photo taken by the DEA in San Luis, Arizona. REUTERS/DEA/Handout

The interior of a cross border tunnel is pictured in this undated handout photo taken by the DEA in San Luis, Arizona. REUTERS/DEA/Handout

The US entryway of a cross border tunnel was located in a storage room inside a business, along with 55 gallon drums filled with dirt and soil from excavation sitting on the side are pictured in this undated handout photo taken by the DEA in San...more

Members of the media wait for their turn to film the entrance to a tunnel under construction found by soldiers at a recycling plant at the Otay Mesa industrial park in Tijuana July 12, 2012. REUTERS/Stringer

A soldier stands guard next to packages of marijuana at a cross border tunnel in Tijuana July 12, 2012. REUTERS/Jorge Duenes

A soldier stands next to debris at a recycling plant where a tunnel under construction was found at the Otay Mesa industrial park in Tijuana July 12, 2012. REUTERS/Stringer

A view of the entrance to a tunnel under construction found by soldiers at a recycling plant at the Otay Mesa industrial park in Tijuana July 12, 2012. REUTERS/Stringer

A soldier stands next to a federal agent (R) inspecting the entrance to a tunnel under construction found by soldiers at a recycling plant at the Otay Mesa industrial park in Tijuana July 12, 2012. REUTERS/Stringer

U.S. Immigration and Customs Enforcement (ICE) photograph released on March 1, 2012 shows an underground drug smuggling tunnel from Mexico into Nogales, Arizona. REUTERS/U.S. Immigration and Customs Enforcement (ICE)/ Handout

U.S. Immigration and Customs Enforcement (ICE) photograph released on March 1, 2012 shows an underground drug smuggling tunnel from Mexico into Nogales, Arizona. REUTERS/U.S. Immigration and Customs Enforcement (ICE)/ Handout

A Mexican soldier looks down into a tunnel found under the Mexico-U.S. border in Tijuana, November 30, 2011. The tunnel, equipped with electric rail cars, ran from California from Mexico and authorities from both countries seized more than 32 tons of...more

A soldier looks into a tunnel found under the Mexico-U.S. border in Tijuana, November 30, 2011. REUTERS/Jorge Duenes

Plywood shoring with a built-in makeshift ladder at the entrance to a drug smuggling tunnel from Mexico uncovered by the U.S. Border Patrol in Nogales, Arizona. Photo released November 22, 2011. REUTERS/U.S. Customs and Border Protection

A soldier opens the access to a tunnel as others stand guard near packages containing marijuana during a presentation to the media in Tijuana, November 16, 2011. REUTERS/Jorge Duenes

A view of the U.S. entrance to a 400-yard long cross-border tunnel after authorities recovered 14 tons of marijuana from warehouses in Otay Mesa industrial park and Tijuana, Mexico, in Otay Mesa, California, November 16, 2011. REUTERS/Handout more

A journalist walks through a tunnel during a presentation to the media in Tijuana, November 16, 2011. REUTERS/Jorge Duenes

An agent from the U.S. Immigration and Customs Enforcement stands guard in front of an industrial building near the Mexican border in Otay Mesa, California, November 3, 2010. REUTERS/Mike Blake

Packs of marijuana are stored in a tunnel in Tijuana, November 3, 2010. REUTERS/Jorge Duenes

An image of the Virgin of Guadalupe is seen in a tunnel, nearly a mile long running into California from Tecate, Mexico, December 4, 2007. REUTERS/Jorge Duenes

A sophisticated smugglers' tunnel, fitted with lights, water pumps and a ventilation system, running under the Arizona border from Mexico found by U.S. border police, May 9, 2011, REUTERS/U.S. Border Patrol

The entrance to a long tunnel inside a warehouse near the Mexican border in Otay Mesa, California, November 3, 2010. REUTERS/Nelvin C. Cepeda/San Diego Union-Tribune/Pool

One of 26 bundles of marijuana found inside a drug smuggling tunnel from Mexico uncovered by the U.S. Border Patrol in Nogales, Arizona, November 22, 2011. REUTERS/U.S. Customs and Border Protection

Packages containing marijuana sit next to a tunnel found under the Mexico-U.S. border in Tijuana, November 29, 2011. REUTERS/Mexico Police

Local police stand guard near a hole that exposed a tunnel in Tijuana August 2, 2011. Authorities discovered the tunnel near another tunnel that had been sealed two years ago. REUTERS/Jorge Duenes

A Mexican soldier flashes his torchlight inside a tunnel the length of six football fields, in Tijuana, November 3, 2010. REUTERS/Jorge Duenes

An entrance to a tunnel found under the U.S.-Mexico border, in San Diego, November 25, 2010. REUTERS/U.S. Immigration and Customs Enforcement

Soldiers stand guard in an incomplete drug tunnel, which has its entrance hidden in a house under construction, in Tijuana, August 12, 2011. REUTERS/Jorge Duenes

A journalist crawls in a cross border tunnel located by the Mexican army at a warehouse in Tijuana July 12, 2012. REUTERS/Jorge Duenes

A view of a cross border tunnel located by the army at a warehouse is seen in Tijuana July 12, 2012. REUTERS/Jorge Duenes

A journalist climbs the shaft of a cross border tunnel located by the Mexican army at a warehouse in Tijuana July 12, 2012. REUTERS/Jorge Duenes

A reporter uses a torch to light marijuana packages inside a truck parked at a warehouse, where the Mexican army located a cross border tunnel, in Tijuana July 12, 2012. REUTERS/Jorge Duenes