At least three people died on Saturday (Sep 25) and multiple passengers were injured after seven cars of an Amtrak train went off the rails in the US state of Montana.
The National Transportation Safety Board said late on Saturday it will investigate the incident.
People trapped aboard soon after the derailment have all been taken off the train, said an official at the Liberty County Sheriff's Office, who spoke on condition of anonymity.
There were multiple injuries but no final count, the official added.
The cause of the incident was not immediately clear.
The Seattle-bound Empire Builder train had about 146 passengers and 16 crew aboard when seven cars derailed near Joplin, Amtrak said.
"Amtrak is working with the local authorities to transport injured passengers, and safely evacuate all other passengers," the firm said in a statement.
The 10-car train with two locomotives had departed from Chicago.
Footage posted on social media showed people waiting by the tracks, luggage strewn next to them, and several train carriages could be seen listing off the rails with at least one toppled onto its side.
Montana's Disaster and Emergency Services coordinator told the New York Times that "well over 50 people had been injured".