Federal authorities in San Diego this week announced they have discovered the longest tunnel ever found beneath the US-Mexico border, extending more than three quarters of a mile to a small industrial building in Tijuana.

The Customs and Border Protection office reported that the tunnel features a rail system with trolleys, air ventilation, high voltage electrical cables and panels, an elevator at the tunnel entrance, and a drainage system.

After the discovery in August, Mexican police identified the entrance to the tunnel and members of the San Diego Tunnel Task Force developed a “mapping” of the passage as it did not have a way out in the United States, the patrol said.

The tunnel is a total of 4,309 feet long and breaks all records. The longest tunnel that had previously been discovered was also found in San Diego in 2014 and was 2,966 feet long when it was closed.

This new tunnel is approximately 5’6” feet high and 2 feet wide, and runs at an average depth of 70 feet below the surface, authorities said.

Agents discovered several hundred sandbags blocking the suspected exit of the tunnel in the Otay Mesa warehouse district of South San Diego.

There were no arrests or seizures of drugs.

An incomplete branch of the tunnel that extended more than 3,500 feet, which authorities say would mean that drug traffickers blocked an initial exit and were building another tunnel in a different direction.

A Border Patrol spokesman commented that for some reason, those who excavated the tunnel seemed to have found a problem where the tunnel was initially headed, and then chose another direction to continue.