Mexican authorities have discovered a sophisticated smuggling tunnel equipped with electricity and ventilation not far from the Nogales port of entry into Arizona, U.S. and Mexican officials said Friday.

The Mexican army said the tunnel was found Thursday after authorities received an anonymous call in the border city of Nogales, Sonora, south of Arizona. U.S. law enforcement officials confirmed that the Mexican military had discovered the football field-long tunnel with elaborate electricity and ventilation systems.

U.S. Border Patrol spokesman Victor Brabble said the tunnel did not cross into the U.S.

The army said the anonymous caller was reporting gunmen standing outside a two-story house in a hilly neighborhood near the international bridge where motorists travel between Mexico and the United States.