An incomplete underground tunnel was discovered beneath a parking lot in Nogales on Wednesday, according to a press release issued by Customs and Border Protection (CBP).
Officials from the Tucson Sector of Customs and Border Patrol, along with members of Mexico's Federal Police, were conducting a "cooperative bi-national tunnel sweep" when they found the incomplete tunnel on May 29.
"The tunnel’s entry point was found several meters below street level inside a legitimate cross-border storm drain that runs into the U.S. from Mexico," CBP's press release reads.
According to CBP, the tunnel was located approximately 75 yards west of the Port of Nogales at the DeConcini Crossing.
It extended 12 feet into the United States, and five feet into Mexico, officials say.
While no suspects have been arrested in connection to the tunnel's construction, Border Patrol agents did find "various digging and cutting tools" underground.
"Authorities on both sides of the border continue to monitor and inspect the incomplete tunnel until it is secured and remediated," CBP said in the press statement.