Photo: ICE. A specialized camera was deployed 25 feet underground to investigate the gap revealing the cross-border tunnel.

SAN LUIS, Ariz. – Special agents with U.S. Immigration and Customs Enforcement’s (ICE) Homeland Security Investigations (HSI) discovered an unfinished cross-border tunnel Tuesday after several days digging in the sandy Sonoran desert terrain outside of Yuma, Arizona where a sinkhole had been discovered in an area where tunneling was suspected.

Photo: ICE. This tunnel has water pipers, rails, and extensive shoring to to support it under the sandy desert soil.

The U.S. portion of the tunnel reaches from the Los Olivos neighborhood in San Luis, Arizona, past the Mexican border and more than 1,300 feet under the fence extending  to Calle 10  in San Luis, Mexico.

The tunnel is 3 feet wide and 4 feet high and has ventilation, water pipes, electrical wiring, a railway system, and a reinforced roof and sides. The tunnel was not yet finished, and there was no exit on the United States end of the tunnel.

“This appears to be the most sophisticated tunnel in U.S. history, and certainly the most sophisticated I’ve seen in my career,” said Carl E Landrum, acting chief patrol agent, Yuma Sector.

In mid-July, federal agents discovered a sinkhole along the U.S./Mexico border between the primary and secondary border fences. HSI special agents responded to the area and observed the sinkhole was in line with the area of an ongoing tunnel investigation. With the assistance of federal partners, on July 27, Yuma Sector Border Patrol commenced drilling near the sinkhole site.

They soon discovered pieces of wood and water hoses were underground, as well as a void. A specialized camera was lowered 25 feet underground to investigate the gap, revealing the cross-border tunnel.