There were no injuries reported in the mudslide that knocked off the dining car and two coach cars, the last three railcars on the train, said Gus Melonas, a spokesman for Burlington Northern Santa Fe, which owns the tracks.
But even without injuries, it was a terrifying train ride for the passengers on board.
"I was asleep at the time, but the little boys next to me started screaming," said one passenger, Cristina Airaghi of San Francisco. "The landslide hit the car in front of us, and then you could hear the dishes and stuff crash from the dining car."
Another passenger, Jim Pruitt of Spokane, said, "I got up and started walking to the end of the car. ... I look down and you could see the wheels weren't on the track."
Passengers say the conductor then let everyone know what happened and that they weren't in any danger.
"You're looking and you're trying to see if the car ahead of you is OK and trying to see if car behind you is OK, and that was kind of frightening because you want everybody to get off safely," said passenger Sherry Brooks of Chicago. "I always think about the landslides when we come through the mountains but never in a million years ... "
The train was travelling south from Everett on the way to Seattle when the slide hit around 8:30 a.m., Melonas said. The train, known as the Empire Builder, started Friday in Chicago.
None of the 86 passengers or 11 crew members on board were injured, Amtrak spokesman Marc Magliari confirmed.
The derailed cars were disconnected, and the passengers were taken to Mukilteo, where they were transferred to a bus bound for Seattle, according to BNSF and Amtrak.
The cause of the slide is under investigation by Amtrak and BNSF officials.
It was not immediately clear how long Amtrak passenger service would be affected, Magliari said.
Washington state has been plagued by mudslides this winter and spring, repeatedly closing tracks that carry Amtrak trains, plus freight and commuter lines.
The tracks where the Empire Builder was damaged were closed as recently as March 21, due to mudslides.
A freight train derailed on the same stretch of tracks in October.
"This has been one of the most problematic years we've faced, historically," Melonas said. "It's due to day after day after day of successive rainfall."
BNSF is working on solutions to stop mudslides in the area, Melonas said.