Massive smuggling tunnel in San Diego

U.S. Immigration and Customs Enforcement/AP

View of a recently-discovered tunnel linking warehouses in Tijuana and San Diego to smuggle drugs, Oct. 30, 2013.

The tunnel is equipped with electricity, ventilation and a rail system, U.S. authorities said Oct. 31, making it one of the more sophisticated secret passages discovered along the U.S.-Mexico border.

Read more: Major drug tunnel found on U.S.-Mexico border; 3 arrested

Paul Caffrey/U.S. Immigration and Customs Enforcement/AP

Agents inspect some of more than eight tons of marijuana and cocaine seized from a tunnel designed to smuggle drugs from Tijuana, Mexico, to San Diego.

U.S. Immigration Custom Enforcement Agent-In-Charge Derek Benner describes elements of a 1,760 foot cross-border tunnel used for drug smuggling in the Otay Mesa area of San Diego, Oct. 31, 2013.

U.S. Immigration and Customs Enforcement agents in a tunnel designed to smuggle drugs from Tijuana, Mexico, to San Diego, Oct. 31, 2013.

A Border Patrol vehicle passes by the front of the industrial park office where a 1,760 foot cross-border tunnel used for drug smuggling was busted by federal authorities in the Otay Mesa area of San Diego Thursday, Oct. 31, 2013.

U.S. Attorney for the Southern District of California, Laura Duffy talks about the investigation leading to the discovery of a 1,760 foot cross-border tunnel in San Diego.

U.S. Attorney for the Southern District of California Laura Duffy, right, and an assistant walk down the loading dock ramp of a business where authorities found the 1,760 foot cross-border tunnel.

San Diego Police Chief William Lansdowne, second from left, and other law enforcement officials approach the door of an office where authorities discovered a 1,760 foot cross-border drug smuggling tunnel, Oct. 31, 2013.

Bales of some of more than eight tons of marijuana and cocaine seized from a tunnel designed to smuggle drugs from Tijuana, Mexico, to San Diego, Oct. 31, 2013.

Agents with bales of some of more than eight tons of marijuana and cocaine seized from a tunnel designed to smuggle drugs from Tijuana, Mexico, to San Diego, Oct. 31, 2013.