Thirty-one people, all believed to be tunnel workers, have been rescued after a partial collapse in an under construction wastewater tunnel in Los Angeles.

The Los Angeles Fire Department (LADF said none of the tunnel workers had “visible injury” and no-one was missing.

More than 100 firefighters attended the rescue in the city’s Wilmington district.

The LADF said the collapse in the 5.5m-diameter tunnel, being constructed for municipal wastewater management, occurred at an undetermined depth at a horizontal excavation site about 8-10km south of the sole access portal.

“The precise number of workers trapped behind the collapse has yet to confirmed. Preliminary reports are that the trapped workers were able to scramble with some effort over a 12-15ft (3.6-4.5m) tall (undetermined length) pile of loose soil, to meet several co-workers on the other side of the collapse and be shuttled several at a time by tunnel vehicle to the entry/access point more than five miles distant,” the LADF said.

During the rescue the media were instructed to keep helicopters 1,600m away from the site as the excessive noise was interfering with the ability of rescue personnel to effectively communicate face-to-face or via radio at ground level.