File-This 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)