John Bacon

USA TODAY

A sophisticated tunnel linked to a major drug cartel has been discovered between San Diego and Tijuana, Mexico, authorities in Mexico say.

The tunnel extends from a location near the Otay Mesa Port of Entry in San Diego to Tijuana's Garita de Otay neighborhood, the Mexican Attorney General's Office said in a statement. Photos show rail tracks running through a lit tunnel framed in wooden posts. A second, unfinished tunnel also was found.

“Presumably, one of these tunnels was being used by a criminal organization operating in the state of Sinaloa for smuggling drugs into the United States,” according to the statement. The U.S. Consulate, the statement said, provided "reliable information" that a cartel was reactivating the tunnels.

The State Department did not immediately respond to a USA TODAY request for more information.

Mexican authorities said the tunnels were hidden with cinder blocks and metal doors. The length of the tunnels was not released.

Discovery of drug tunnels in the area is nothing new — in April a half-mile tunnel was found between the cities. Six people were arrested and authorities seized a ton of cocaine and more than seven tons of marijuana, said Laura Duffy, U.S. attorney for the Southern District of California. The cocaine alone was valued at around $22 million.