MEXICO CITY (Reuters) - U.S. anti-narcotics agents have discovered a drug-smugglers' tunnel running under the U.S.-Mexico border and equipped with a rail track, electricity and ventilation system, the U.S. Department of Justice said.

       The so-called "narco-tunnel" led from the Mexican city of Tijuana to a warehouse 300 feet from the border in San Diego, California, the department said in a statement.

       U.S. authorities arrested six people for their alleged involvement in the drug-running scheme. They are accused of conspiring to distribute cocaine, heroin and methamphetamine, among other crimes.

       "There is no more light at the end of this narco-tunnel," said U.S. Attorney Randy Grossman in the statement.

       The tunnel, estimated to be more than 1,750 feet (530 m) long, was also fitted out with reinforced walls.

       The attorney general's office for the Mexican state of Baja California, where Tijuana is located, told Reuters U.S. authorities had notified them of the discovery Sunday, two days after it was found.

       Mexico's Sinaloa cartel, led for years by Joaquin "El Chapo" Guzman, is responsible for many of these tunnels, found in warehouses, homes and businesses, Mexican authorities said.

       Since 1993, close to 100 tunnels have been found in the same area, most recently in March 2020, U.S. prosecutors said.

       The tunnel was one of the largest located in the region, the Baja California attorney general's office said

       Mexico's federal prosecutor's office did not respond to a request for comment.

       (Reporting by Lizbeth Diaz and Kylie Madry, Editing by Angus MacSwan)