A report of a possible sinkhole led authorities to a cross-border tunnel near San Luis.

Contractors working on the border wall project had been moving soil in the area when they uncovered plywood and boards. The lumber was later determined to be possible tunnel shoring. Further excavation of the site west of the San Luis Port of Entry led to an incomplete cross-border tunnel that was 8 to 12 feet below the surface. Yuma Sector Border Patrol agents , along with special agents of Homeland Security Investigations , coordinated with Mexican authorities and military and located the entrance to the tunnel in San Luis Rio Colorado , Sonora ,  Mexico approximately 10-12 feet south of the original hole. Law enforcement on both sides of the border are continuing to investigate the tunnel.