The Washington State Department of Transportation posted a photo on Twitter showing train cars on the highway and dangling off the overpass on Interstate 5 south of Seattle.
All SB lanes of I-5 blocked near Mounts Road in Pierce County due to derailed train car. Avoid area! pic.twitter.com/SBH7dCc6yg— WSDOT Tacoma Traffic (@wsdot_tacoma) December 18, 2017
The incident is being handled as a mass casualty incident, according to KIRO 7, a CBS affiliate.
At least six individuals died in the crash, The Seattle Times reported.
The cause of the derailment has not been determined.
Photos from scene of amtrak passenger train derailment pic.twitter.com/gd09MzLCC6— Pierce Co Sheriff (@PierceSheriff) December 18, 2017
Brooke Bova, a Washington State Patrol spokeswoman, said rescue efforts were ongoing but declined to provide additional information about injuries and fatalities.
“We’re asking people to please stay off of I-5 if you don’t need to be here,” Bova said at a news conference, adding that two northbound lanes of Interstate 5 were clear for travel.
At another press briefing later in the day, Bova said there were “multiple casualties” in the derailment, but authorities were not performing "rescue operations at this time."
“Unfortunately, we’re not confirming numbers at this time,” she added, referring to casualties.
Thirteen train cars jumped the track when the train was derailed.
National Transportation Safety Board (NTSB) member Bella Dinh-Zarr told reporters in Washington, D.C., that a "go team" would be deployed to investigate the derailment.
The NTSB will work with both Amtrak and local officials, Dinh-Zarr said, adding that several members of the investigative team will arrive Monday.
Dinh-Zarr also said it's "too early to know" if the train's speed played a role in the crash.
This breaking news report was last updated at 3:34 p.m.