COLTON, Calif.—A Union Pacific freight train carrying lumber derailed in Southern California on Monday, sending 13 rail cars and three locomotives off the tracks. The derailment occurred around 7:30 a.m. near Colton, in San Bernardino County east of Los Angeles, according to Union Pacific. A contractor who was helping with cleanup efforts was injured, said Union Pacific spokesperson Robynn Tysver. The extent of the person’s injuries wasn’t immediately known. TV helicopter footage showed several rail cars flipped over with lumber spilled across the tracks. One of the cars carrying wood caught fire in the derailment, but the flames were quickly extinguished, Tysver said. The Colton Police Department and San Bernardino County Fire Department responded. The cause of the derailment is under investigation.