(AP) - PHOENIX -An incomplete tunnel found stretching from Mexico to Arizona appears to be “the most sophisticated tunnel in U.S. history,” authorities said.
The tunnel intended for smuggling ran from a neighborhood in San Luis Río Colorado, Mexico, to San Luis, Arizona, where it stopped short of reaching the surface.
It was built in an area that's not conducive to tunnels because of the terrain, and it had a ventilation system, water lines, electrical wiring, a rail system and extensive reinforcement, federal officials say.
Homeland Security Investigations (HSI) started excavating around the tunnel in late July after someone reported a sinkhole near the border wall.
HSI already had reports of potential tunnel activity in that area and the agency began drilling, according to Angel Ortiz, assistant special agent in charge for Homeland Security Investigations in Yuma. HSI is a division of U.S. Immigration and Customs Enforcement.
A camera was sent 25 feet underground, and the tunnel was discovered on Tuesday. The tunnel measured three feet wide and four feet high.
Investigators don't know what exactly the tunnel would have been used for, since it was incomplete. Smugglers have been using tunnels to get drugs and people across the border for decades.
HSI continues to investigate the tunnel found Tuesday.