The trapped workers were shuttled back to the tunnel’s entry point, more than 8km away from the affected area, after they escaped the collapsed section and met several co-workers in the unaffected part of the tunnel, the Los Angeles fire department said in a statement.

The tunnel, which had a diameter of 5.5m, trapped 27 individuals, while four workers entered the damaged section to assist with rescue, LA fire chief Ronnie Villanueva told reporters in a media briefing.

“The workers had to climb through debris. They had to make themselves out through”, before they were assisted out, Villanueva said.

Robert Ferrante, chief engineer and general manager of Los Angeles county sanitation districts, told the briefing that a section of the already built part of the tunnel experienced squeezing ground conditions and partially collapsed.

“LAFD has just reported that all workers who were trapped in the tunnel in Wilmington are now out and accounted for. I just spoke with many of the workers who were trapped. Thank you to all of our brave first responders who acted immediately,” Los Angeles mayor Karen Bass said in a post on X.

The collapsed section was a part of the Los Angeles County’s Clearwater project, where the new 7-mile tunnel is being built to upgrade the region’s sewer system, officials added.