Thirty-one men working in a massive underground tunnel in Los Angeles were rescued Wednesday night after a portion of the structure collapsed, officials said.

Fire officials said the trapped workers managed to escape by scrambling over a roughly 12- to 15-foot mound of loose soil to reach four co-workers who had gone in to help.

The workers on Wednesday night were 400 feet underground and near the coast, as much as 6 miles away from the only entrance.