An explosion inside a shipping container at the world's largest railyard prompted evacuations in western Nebraska Thursday because of the toxic smoke generated when one of the chemicals aboard caught fire.

Around noon, an explosion occurred inside an intermodal container on a railcar at Union Pacific's Bailey Yard in North Platte, though it wasn't clear what caused the explosion, railroad spokeswoman Robynn Tysver said. No one was injured, and no cars derailed.

Authorities evacuated everyone within a four-mile radius of the railyard, which is about 280 miles west of Omaha, was evacuated because of the smoke, and U.S. Highway 30 was closed between North Platte and Hershey. Interstate 80 wasn't affected by the smoke.

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An explosion at a Nebraska railyard has prompted evacuations due to heavy toxic smoke. 

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The North Platte Fire Department said in a post on X that the evacuations were done because of the fire at the railyard involved "heavy toxic smoke." Fire officials didn’t immediately respond to a call seeking more details.

One of the containers involved was carrying perchloric acid, which is used in explosives as well as a variety of food and drug products, Tysver said.

Railroad safety has been a key concern nationwide ever since a Norfolk Southern train derailed and caught fire in eastern Ohio. That derailment prompted evacuations and calls for reform from members of Congress and regulators.