‘Tonight we were lucky,’ Los Angeles Fire Department’s Interim Fire Chief Ronnie Villanueva said.

First responders rescued 31 trapped workers from a collapsed tunnel in Los Angeles on July 9, officials said.

Construction workers were inside the tunnel at North Figueroa Street in Wilmington when its structural lining failed about six miles in from the entrance, Los Angeles Fire Department’s Interim Fire Chief Ronnie Villanueva said at a news conference.

Crews responded to the scene just before 8 p.m. local time and safely removed the workers from the tunnel without any visible injuries, LAFD said.

The 18-foot-wide tunnel is being constructed for municipal wastewater management, LAFD said.

More than 100 first responders were on site to assist in the rescue, Villanueva said.

“Tonight we were lucky,” Villanueva said.

Los Angeles Mayor Karen Bass, who also spoke at the news conference, thanked first responders and called the rescue a “victory.”

Workers climbed over debris to get out of collapsed tunnel

Villanueva said 27 workers were inside the tunnel when it collapsed, and four more went inside to help.

“The workers had to climb through debris,” Villanueva said. “They had to make themselves out through and then rescuers actually came to them to assist them out.”

They were “shaken up” but “alive and happy,” Janice Hahn, a member of the Los Angeles County Board of Supervisors for the 4th district, said during the news conference.

“It was quite traumatic for them to go through that, so we thank them,” Hahn said.

What caused LA tunnel collapse?

Hahn said the Los Angeles County Sanitation Districts will investigate what caused the tunnel to collapse and “do everything we can to prevent anything else like this from happening.”

The workers were operating a tunnel boring machine when the collapse occurred, Robert Ferrante, chief engineer and general manager for the LACSD, said at the news conference.

“Anytime you tunnel underground, you encounter different conditions in different locations,” Ferrante said. “And obviously there was a location that squeezed the tunnel and forced it to partially collapse.”

The tunnel construction is part of Los Angeles’ Clearwater Project, officials said. The project is overhauling some of the city’s existing sewage waste tunnels and is intended to be completed in 2027.

This story was updated to add new information.

Melina Khan is a national trending reporter for USA TODAY. She can be reached at melina.khan@usatoday.com.