A wireless, camera-equipped robot is displayed by the U.S. Border Patrol during a briefing in Nogales, Ariz., Tuesday, Jan. 14, 2014. With more than 75 underground drug smuggling tunnels found along the border since 2008, mostly in California and Arizona, the U.S. Border Patrol is utilizing the robots to assist in their search. (AP Photo/Brian Skoloff)

U.S. Border Patrol Agent Ryan Grimm demonstrates how a robot is used to navigate a drainage canal along the border fence during a briefing in Nogales, Ariz., Tuesday, Jan. 14, 2014. With more than 75 underground drug smuggling tunnels found along the border since 2008, mostly in California and Arizona, the Border Patrol is utilizing the wireless, camera-equipped robot, to search underground while keeping agents safer. (AP Photo/Brian Skoloff)

This July 8, 2004 file photo shows a Mexican federal agent crawls through a hidden tunnel, presumably used to transport drugs from Mexico to the U.S. The job of searching these networks can be dangerous, so the U.S. Border Patrol is unveiling its latest technology in the underground war, a wireless, camera-equipped robot that can do the job in a fraction of the time. (AP Photo/David Maung)

his July 12, 2012 file photo shows the entrance to a cross border illegal tunnel lit by a lamp after it was found underneath a bathroom sink by the Mexican army inside a warehouse in Tijuana, Mexico. More than 75 such underground passages have been found along the border since 2008, concentrated largely in California and Arizona. The job of searching these networks can be dangerous, so the U.S. Border Patrol is unveiling its latest technology in the underground war, a wireless, camera-equipped robot that can do the job in a fraction of the time. (AP Photo/Alejandro Cossio)

A news photographer walks inside a tunnel in the northern border city of Tijuana, Mexico Wednesday Nov. 30, 2011. A day earlier, the tunnel was discovered by U.S. authorities in San Diego’s Otay Mesa area, the latest in a spate of secret passages found to smuggle drugs from Mexico. This tunnel is a 600-yard passage linking warehouses in San Diego and Tijuana and is equipped with lighting and ventilation. (AP Photo/Alex Cossio)

A Mexican army soldier stands next to an elevator shaft that lowers into a tunnel in the northern border city of Tijuana, Mexico Wednesday Nov. 30, 2011. U.S. authorities said they discovered a new cross-border tunnel Tuesday, the latest in a spate of secret passages found to smuggle drugs from Mexico. The tunnel was found in San Diego’s Otay Mesa area, a warehouse district across the border from Tijuana, said Lauren Mack, a spokeswoman for U.S. Immigration and Customs Enforcement. (AP Photo/Alex Cossio)

Mexican Army soldiers custody the entrance of a clandestine tunnel connecting warehouses on either side of California’s border with Mexico in Tijuana, Thursday, Nov. 4, 2010. Federal authorities in San Diego made one of the largest marijuana seizures in the United States, confiscating more than 20 tons of pot that was smuggled to the country through the underground tunnel that had lighting, ventilation and a rail system to send loads of illegal drugs into California. Mexican authorities also seized more than four tons of drug from the warehouse on their side. (AP Photo/Guillermo Arias)

An altar is seen at the bottom of a 9 meters deep (29 feet), 122 meters long (400 ft) tunnel found by the Army on a house near the US-Mexico border in Tijuana, Mexico, Saturday, Nov. 7, 2009.(AP Photo/Guillermo Arias)

A cameraman takes footage inside a tunnel near the US-Mexico border in Tijuana, Mexico, Tuesday, Oct. 27, 2009. Mexican soldiers have discovered a secret tunnel complete with electricity and an air supply that may have been planned for smuggling migrants or drugs under the U.S. border into San Diego (AP Photo/Guillermo Arias)

Members of the media stand outside a tunnel near the US-Mexico border in Tijuana, in Mexico, Tuesday, Oct. 27, 2009. Mexican soldiers have discovered a secret tunnel complete with electricity and an air supply that may have been planned for smuggling migrants or drugs under the U.S. border into San Diego (AP Photo/Guillermo Arias)

Soldiers talk to a suspect outside the house were the army found a tunnel under construction 40 yards from the border with the US in Tijuana, Mexico, Wednesday, July 8, 2009. (AP Photo/Guillermo Arias)

Mexican federal agents stand at the entrance to a hidden tunnel, presumably used to transport drugs from Mexico to the U.S., on Thursday, July 8, 2004 in Tijuana, Mexico. The tunnel, which starts in an abandoned house in Tijuana, crosses under the U.S. border wall. (AP Photo/David Maung)

Wheelbarrows sit on the ground of a sophisticated clandestine tunnel that passes under the US-Mexico border on Wednesday, Jan. 25, 2006 in Tijuana, Mexico. 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 wall. (AP Photo/David Maung)

Soldiers use an elevator to descend journalists to a 9 meters deep (29 feet), 122 meters long (400 ft) tunnel found by the Army inside a house near the US-Mexico border in Tijuana, Mexico, Saturday, Nov. 7, 2009. Six suspects were arrested. (AP Photo/Guillermo Arias)

This Nov. 4, 2010 file photo shows a Mexican Army soldier using a flashlight to 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. The job of searching these networks can be dangerous, so the U.S. Border Patrol is unveiling its latest technology in the underground war, a wireless, camera-equipped robot that can do the job in a fraction of the time. (AP Photo/Guillermo Arias)

This June 4, 2010 file photo shows Mexican army soldiers standing guard next to a tunnel at the border wall in Tijuana, Mexico. More than 75 such underground passages have been found along the border since 2008, concentrated largely in California and Arizona. The job of searching these networks can be dangerous, so the U.S. Border Patrol is unveiling its latest technology in the underground war, a wireless, camera-equipped robot that can do the job in a fraction of the time. (AP Photo,File)