COLTON, Calif. (AP) — A Union Pacific freight train carrying lumber derailed in Southern California, sending 13 rail cars and three locomotives off the tracks.

The derailment occurred around 7:30 a.m. Monday near Colton, in San Bernardino County.

Union Pacific says a contractor who was helping with cleanup efforts was injured.

The extent of the person’s injuries wasn’t immediately known.

TV helicopter footage shows several rail cars flipped over with lumber spilled across the tracks. Officials say one of the cars carrying wood caught fire in the derailment, but the flames were quickly extinguished.

The cause of the derailment is under investigation.