At least three people have been killed and 50 others hurt after a train came off the tracks in the state of Montana.
Several carriages from the Amtrak Empire Builder passenger service derailed at about 16:00 local time (22:00 GMT) near the town of Joplin.
Amtrak said there were approximately 141 passengers and 16 crew aboard the Chicago to Seattle service.
Images on social media show train cars on their sides and luggage strewn on the ground with people standing nearby.
Passenger Megan Vandervest, who was heading to see a friend in Seattle, told the New York Times she was woken up by the derailment, which felt like "extreme turbulence on plane."
Rescuers have been working to evacuate passengers, Amtrack said.
In a tweet, state Senator Steve Daines said he was "closely monitoring this situation".
"I am thankful for the first responders already on the scene and praying for the safety of all involved," he added.
The US National Transportation Safety Board has launched an investigation into the incident.
Through derailments of Amtrak trains are rare, there have been several in recent years.
In 2018, three people were killed when an Amtrak train travelled on to the wrong track and hit a parked freight train.
BDST: 1316 HRS, SEP 26, 2021