A train has derailed and fallen onto a highway below around 40 miles south of Seattle causing "multiple fatalities".
Seventy-seven people have been taken to hospital, including several motorists. The Seattle Times have reported that at least six people are dead – this figure is likely to rise.
The official Washington State Department of Transportation Twitter account posted a picture of the incident and warned people to stay area from the area.
Chris Karnes, a passenger on the train, told CBS News: "We had just passed the city of DuPont and it seemed like we were going around a curve."
"All of a sudden, we felt this rocking and creaking noise, and it felt like we were heading down a hill. 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."
All southbound lanes of Interstate 5 are closed south of Joint Base Lewis-McChord. Pierce County Sheriff department spokesperson Ed Troyer said there are "multiple fatalities" and injuries following the crash but did not specify any further.
The train is believed to have been travelling at speeds of up to 80mph (127kmh) at the time. According to Reuters, the derailment occurred on the first day that Amtrak trains began using a new track between Tacoma and Olympia as part of plans to reduce travel time.
Karnes added: "The tracks for this line were supposed to be upgraded to be able to handle higher speeds. I'm not sure what happened at this juncture."
Governor Jay Inslee said: "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."
The National Transportation Safety Board said it was "gathering information" about the accident.
Amtrak added in a statement: "Amtrak is aware of an incident with Train 501, Cascades service from Seattle to Portland. Emergency services are on the scene and Amtrak management is responding.
"Some injuries are reported. Amtrak service south of Seattle is temporarily suspended. Service from Seattle to points north and east is continuing to operate."