U.S. authorities on Wednesday announced the discovery of the longest smuggling tunnel ever found on the Southwest border, stretching more than three-quarters of a mile from Tijuana, Mexico, into the San Diego area.

U.S. Customs and Border Protection said the tunnel originates in an industrial area in Mexico and extends a total of 4,309 feet. (1,313 meters).

It features an extensive rail/cart system, forced air ventilation, high voltage electrical cables and panels, an elevator at the tunnel entrance, and a complex drainage system, the agency said.

“While subterranean tunnels are not a new occurrence along the California-Mexico border, the sophistication and length of this particular tunnel demonstrates the time-consuming efforts transnational criminal organizations will undertake to facilitate cross-border smuggling,” said Cardell T. Morant, acting special agent in charge of Homeland Security Investigations in San Diego.

Following the discovery in August, Mexican law enforcement identified the tunnel entrance and members of the San Diego Tunnel Task Force began mapping the tunnel from Mexico, the agency said.

The next longest tunnel in the U.S. was discovered in San Diego in 2014. It was 2,966 feet (904 meters) long.

The newly discovered tunnel is about 5.5 feet (1.68 meters) tall and 2 feet (0.61 meters) wide and runs at an average depth of 70 feet (21.3 meters) below the surface, officials said.

Agents discovered several hundred sandbags blocking the suspected former exit of the tunnel in the Otay Mesa warehouse district within the U.S.

The discovery did not lead to any arrests or seizures.

(AP)