Original Article Mar 4, 3:28 AM EST Border Patrol discovers tunnel from Nogales to Mexico TUCSON, Ariz. (AP) -- U.S. Border Patrol agents found a recently dug tunnel crossing the border from Mexico to downtown Nogales, Ariz., and arrested several immigrants coming through it. The tunnel was discovered Thursday after agents patrolling Nogales overheard voices coming from a nearby ground-level steel grate. According to a statement released by the U.S. Border Patrol, the agents removed the grate and entered a drainage system, causing several men to flee south through the tunnel toward Mexico. The Border Patrol said the tunnel was dug to get around security obstacles placed in the drainage system.