A 21-car derailment of a Union Pacific freight train in northern Bear Lake County apparently was caused by an improperly loaded hopper car, a railroad spokesman said.

Crews planned to have the southeastern Idaho rail line cleared and reopened by early Thursday afternoon, Union Pacific spokesman Joe Thibodeau said Thursday from Omaha, Neb.Rail traffic in the area was rerouted south through Ogden because of the derailment, which occurred southeast of Soda Springs about 1 p.m. Wednesday on a train en route from Pocatello to North Platte, Neb.

Thibodeau said a hopper car carrying talc on the eastbound train apparently was loaded too heavily on one end. That caused a wheel to jump the track on a curve.

The train was carrying a variety of freight, including a chemical used to make fertilizer. But the chemical did not spill and no injuries were reported.

Thibodeau said no Amtrak trains or routes were affected by the accident.