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,

None of the 31 construction workers rescued in the tunnel sustained visible injuries, according to LAFD. Firefighters said construction workers climbed over a roughly 12 to 15-foot pile of dirt to escape.

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.