Two Union Pacific locomotives and more than 50 cars jumped the track in the Mojave Desert on Monday. They were bound for Long Beach.
According to emailed statements from Union Pacific, the train’s crew was not in the cab at the time of the derailment.
The statements do not explain why and a Union Pacific spokesman declined an interview.
State, local and federal officials are working with Union Pacific to determine what happened.
There were no injuries and iron ore, which is used to make steel, is not hazardous.
Data reported by the Federal Railroad Administration shows last year there was an average of 3 derailments per day in the United States.