SAN DIEGO, Calif. – U.S. authorities on Wednesday announced the discovery of the longest smuggling tunnel ever found on the Southwest border, stretching more than three-quarters of a mile from an industrial site in Tijuana, Mexico, to the San Diego area. The next longest tunnel in the U.S. was discovered in San Diego in 2014. U.S. authorities say they are confident that the tunnel exited in San Diego at one time, based on its trajectory. The latest tunnel was discovered by Mexican authorities in a Tijuana parking lot for cargo trucks, next to the city’s airport. Authorities didn’t say who they believe was behind the tunnel but the area has been a stronghold of Mexico’s Sinaloa cartel.