Approximately 40 train cars were derailed near Picacho Peak in southern Arizona on Monday night. The National Weather Service had issued a severe weather warning for the area.
The crew had reported having to slow down because of rain. There is speculation that the train was hit by a microburst.
No one was injured. The 30 freight cars were empty, according to authorities. Crews are still clearing the cars and repairing the rails.
The train was en route to Los Angeles from Houston, Texas, according to a Union Pacific spokesman.