Sixteen railroad freight cars carrying corn derailed early Wednesday under a key railroad overpass in the northeast Nevada city of Elko, but no injuries were reported and no hazardous materials were involved, authorities said.

The Union Pacific train derailed just before 5 a.m., striking a bridge support pillar and piling grain hoppers against each other and a sound wall, Elko police Lt. Rick Moore said, prompting concerns about the structural integrity of the 12th Street overpass.

The crash near the Humboldt River and an Amtrak passenger train stop spilled corn kernels but "missed the Amtrak kiosk by providence," Moore told The Associated Press.

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Union Pacific spokesperson Robynn Tysver said the cause of the derailment was being investigated and engineers from the Nevada Department of Transportation would inspect the overpass before it would be allowed to reopen.

Moore said cleanup and inspections were expected to take at least 24 hours, snarling vehicle traffic and blocking eastbound and westbound train traffic.

The tracks serve Amtrak passenger trains between Chicago and the San Francisco Bay area. Amtrak spokesman Jason Abrams noted the derailment did not involve an Amtrak train. He said officials expect at least two California Zephyr passenger trains to be delayed.

Moore said it was not clear if any people were nearby when the crash occurred, but said a power pole was knocked down.

Meghin Delaney, spokesperson for Nevada Energy, the main electricity provider in the state, said electric service to nearby homes and businesses was not interrupted.