Some of the carriages from the train – which had been making its first-ever run along a new, faster route – fell on to the highway below, killing at least three people, injuring dozens and crushing two vehicles, authorities said.
Federal investigators say the train was travelling at 80mph (129km/h) in a 30mph zone. Bella Dinh-Zarr, a National Transportation Safety Board member, said at a news conference on Monday night that the event data recorder in the rear locomotive provided information about the train’s speed.
Dinh-Zarr said it was not yet known what caused the train to derail and that “it’s too early to tell” why it was going so fast. She said it was likely that federal investigators would be on the scene for a week or more.
There were 80 passengers and five on-duty crew on board when the train derailed and 13 carriages fell off the tracks. As well as the three confirmed deaths, more than 70 people needed medical care including 10 with serious injuries.
Aleksander Kristiansen, a 24-year-old passenger from Copenhagen, said he had been in the bathroom when the crash occurred and he had been thrown to the ground. When he stood up, the train was shaking, he said.
“I didn’t believe it happened when it happened,” he said.
Kristiansen, who was in Seattle for an exchange programme, said his train car had stopped on a steep embankment, and that he had got out from the back of the car and helped others out.
First responders spent hours searching the train cars, some of which were not safe to enter as they continued to dangle off the overpass.
The new route, which was built to speed up local services, launched on Monday “after weeks of inspection and testing”, officials said.
A track chart from the Washington state department of transportation shows the maximum speed drops from 79mph to 30mph for passenger trains just before the tracks curve to cross the Interstate 5 highway, which is where the train went off the tracks.
The chart, dated 7 February 2017, was submitted to the Federal Railroad Administration in anticipation of the start of passenger services along the new bypass route, which shaves 10 minutes off the trip between Seattle and Portland.
The Washington state governor, Jay Inslee, declared a state of emergency and visited the scene on Monday. He emphasised that the cause of the crash remained unknown.
“There are four things we need to do: express compassion for these families, respect first responders, stay off [Interstate 5] and suspend judgment. No one knows what happened in this incident.”
A few hours after the crash, Donald Trump cited it as a reason to support his infrastructure plan, tweeting: “The train accident that just occurred in DuPont, WA shows more than ever why our soon to be submitted infrastructure plan must be approved quickly. Seven trillion dollars spent in the Middle East while our roads, bridges, tunnels, railways (and more) crumble! Not for long!”
Ten minutes later, he tweeted: “Thoughts and prayers are with everyone involved.”