An aerial view shows the only entrance to an industrial tunnel in the Wilmington neighborhood of Los Angeles on Thursday after a section of the tunnel partially collapsed Wednesday night. (AP Photo/Jae C. Hong)

LOS ANGELES (AP) — After a section of a large industrial tunnel caved in, more than two dozen construction workers who were hundreds of feet below the streets of Los Angeles raced for miles in the dark — clambering over towering debris, terrified of being trapped, according to descriptions by their family members and officials Thursday, a day after the collapse.

Remarkably, all 31 workers escaped to safety Wednesday night and none suffered any major injuries.

Fire Department Chief Ronnie Villanueva said the workers had to make it through the most treacherous part themselves, climbing over more than 12 feet of loose dirt before rescuers could reach them and drive them to the only opening.

The tunnel, which is 18 feet wide and 7 miles long, is under the Wilmington neighborhood, a heavily industrial area filled with oil refineries just north of the Port of Los Angeles. It is a nearly $700 million project that’s designed to carry treated wastewater to the Pacific Ocean.

The workers were 400 feet underground and as much as 6 miles away from the only exit, said Michael Chee, spokesperson for the Los Angeles County Sanitation Districts.

A transport vehicle had taken them in to supervise the operations of a machine that digs out the corridor and then builds the tunnel at the same time and uses the panels that are installed to move itself forward, Chee said.

When they learned of the collapse, they ran back and hopped aboard the transport vehicle that had taken them into the tunnel, but it could only move for a mile before it encountered the debris.

“What we understand is the men who were in front of the collapse had approximately 6 to 8 feet of space above the debris where they were able to clamber over,” Chee said.

After that, the workers — still in the dark, frightened and miles from the opening — continued on foot until rescuers were able to reach them and help them onto vehicles to take them to the shaft where a cage carried them out.

Aerial footage showed a crane hoisting workers out of the tunnel in a yellow cage.

“They’re shaken up,” Chess said, adding that the workers will be taking time to recover and all work has been halted.