The crash caused “multiple deaths” and some motorists were injured when the train fell and struck several vehicles, according to a spokesman for the local sheriff’s office.
The train derailed around 7.30am (3.30pm GMT) in DuPont in Washington state. The Interstate 5 is the major north–south route on the West Coast of America.
A photographs showed an upside-down train car partially crushed on the highway, with a second car dangling off the overpass.
The train, which was scheduled to depart Seattle at 6am (2pm GMT) en route to Portland, Oregon, was the first to run along a new route.
Amtrak trains today began using a new route between the cities of Tacoma and Olympia, according to an October news release from the state’s transportation department.
The new route takes trains along Interstate 5, eliminating a major choke point for passenger trains in Tacoma and allowing trains to reach speeds of 79 mph, the department has said.
It was not immediately clear whether the derailment was connected to the new route.
Amtrak passenger Chris Karnes told local news outlet KIRO 7 that passengers were forced to kick out train windows in order to escape, because emergency doors were not functioning properly following the derailment.
“We had just passed the city of DuPont and it seemed like we were going around a curve,” Karnes said. “All of a sudden, we felt this rocking and creaking noise, and it felt like we were heading down a hill.”
He added: “The next thing we know, we’re being slammed into the front of our seats, windows are breaking, we stop, and there’s water gushing out of the train. People were screaming,” he added.
Amtrak confirmed its train was involved and said “some injuries” had been reported but did not immediately offer further details.
About 70 people were aboard the train, local news media reported, citing the state transportation department.
Authorities warned drivers to avoid the area, and the southbound lanes remained closed.
he National Transportation Safety Board said on Twitter that it was gathering information about the incident.
Washington Governor Jay Inslee tweeted: “Thank you to the first responders on the scene. We’re praying for everyone on board the train, and ask everyone to hold them in your thoughts.”