U.S. Border Patrol agents have uncovered a sophisticated underground tunnel stretching more than 1,000 feet into the United States from Mexico as part of a drug-smuggling operation in Southern California.

U.S. Border Patrol agents shut down the construction of a 2,918-foot-long tunnel connecting Tijuana and San Diego with the aid of Department of Homeland Security officials and Mexican authorities.

Agents have located and disabled an unfinished tunnel stretching from Tijuana into Otay Mesa, extending more than 1,000 feet into the U.S.