Mexican Army Finds New Drug Tunnel at US Border The Mexican army says it has found a new tunnel dug by drug smugglers under the border with the United States. The army says it found the tunnel under construction in a water-purification plant in Tecate, across the border from a mostly rural area of Southern California. Soldiers arrested eight people during the operation and confiscated a small amount of marijuana. The tunnel was about five feet in diameter and 135 yards long, with a concrete floor and ventilation and electric lighting. U.S. and Mexican authorities have discovered a series of similar border tunnels in recent years.