Thirty-one people working in a massive underground tunnel in Los Angeles were rescued Wednesday night after a portion of the structure collapsed, officials said. Those rescued didn’t have any visible injuries,

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.

An industrial tunnel in Los Angeles collapsed partially. None of those rescued had major injuries, authorities said.