The U.S. Border Patrol says its agents and Mexican federal police discovered an incomplete cross-border tunnel under a parking lot in Nogales.
The agency said Friday the tunnel spotted Wednesday was connected to a storm drain that runs into the United States from Mexico.
Border Patrol says the tunnel, as well as digging and cutting tools, was found during a sweep to help prevent illegal movement of contraband and people across the border.
The agency said the tunnel extended 12 feet (4 meters) into the United States and 5 feet (1.5 meters) into Mexico.
The agency said no immediate arrest was made and authorities will secure the tunnel.