An Amtrak passenger train has derailed during its inaugural run along a faster route through Washington state, sending part of the train crashing down onto a major highway and killing an unknown number of passengers, authorities say.
The derailment caused "multiple fatalities," Ed Troyer, a spokesman for the local sheriff's office, told reporters at the scene, though he did not offer a specific number.
Seventy-seven people were transported to hospitals. Four of them were considered "level red" patients with the most severe injuries.
About 78 passengers and five crew members were aboard the train, Amtrak said in a statement.
The derailment occurred on the first day Amtrak trains began using the new inland route between the cities of Tacoma and Olympia, part of a project to reduce travel time, according to an October news release from the state's transportation department.
It was not immediately clear whether the derailment, which came during a busy travel time one week before the Christmas holiday, was connected to the rerouting.
The National Transportation Safety Board was sending a team of investigators to the site, the federal agency said on Twitter.
Washington Governor Jay Inslee declared a state of emergency due to "loss of life, injuries and damage to infrastructure."
US President Donald Trump tweeted that the crash "shows more than ever why our soon-to-be submitted infrastructure plan must be approved quickly". Mr Trump has said he will unveil his long-delayed infrastructure proposal after Congress passes its tax bill.
The derailment was Amtrak's second in Washington state this year. On July 2, a southbound train with more than 250 people aboard derailed in the town of Steilacoom, just a few kilometres north of Monday's crash site. No serious injuries were reported.