Three people were killed when an Amtrak train derailed near Seattle Monday and landed on Interstate 5, the Washington State Patrol said.
The National Transportation Safety Board (NTSB) said in a late night news conference that the train was travelling 80 miles per hour (mph) in a 30 mph zone, NBC News reported.
The NTSB said that data recovered from an event recorder at the rear of the train had provided information on the train's speed at the time of the derailment.
Amtrak said in a statement there were approximately 80 passengers, five crew members and one technician on board the Cascades Train 501, which was on the first day of service for the route. It was operating from Seattle and Portland, Oregon.
At a press conference, a Washington State Patrol spokesman confirmed three dead. Ten were seriously injured, and one was flown to a hospital. There were other injuries as well.
In the time immediately following the accident, authorities had reported at least six people dead, according to the Associated Press.
The Thurston County Sheriff tweeted about a "massive incident involving a train" derailing on the Mounts Road overpass midway between Tacoma and Olympia.
Five cars and two tractor-trailers on the highway were struck after 13 train cars derailed, some piling down off the overpass, around 7:40 a.m. PT, according to police. Several motorists were injured, but no fatalities among motorists were reported.
The train was moving more than 80 mph at the time of the accident. A U.S. official told the AP that track obstruction is seen as a possible cause.
Amtrak "temporarily suspended" service south of Seattle.
About 78 passengers and five crew members were on board. Amtrak recommended anyone with questions about family or friends aboard the train call 800-523-9101.
The mayor of DuPont declared a state of emergency in the city.
Several hours after the incident, Amtrak President and co-CEO Richard Anderson released a statement.
"On behalf of everyone at Amtrak, we are deeply saddened by all that has happened today. We will do everything in our power to support our passengers and crew and their families," Anderson's statement said.
Photojournalist Terry Griffin for Seattle's KIRO 7 said in a tweet that first responders were "treating this as a mass casualty incident."
A notice on the Washington State Department of Transportation's website before the crash said that Monday was the first day for Amtrak's Cascades train to use the route along I-5.
Alex Rozier, a reporter from NBC Seattle affiliate KING-TV, had been on the train reporting on the new route but got off at the previous stop. He said most of the seats were filled in the part of the train he was reporting from.
"It derailed minutes after we got off the train," he said.
Monday marked the first day of public use for the track, which had been upgraded from a freight and military route to passenger rail service. The accident followed what WSDOT described as "weeks of inspection and testing."
The cause of the derailment is under investigation by multiple authorities. The National Transportation Safety Board has dispatched a team of 20 investigators, who will arrive on scene Monday evening and Tuesday morning.
NTSB spokesperson Bella Dinh-Zarr said "it's a little too early to know" whether speed was a factor in the accident or whether the train was outfitted with accident avoidance technology.
President Donald Trump said in a tweet that the accident "shows more than ever why our soon to be submitted infrastructure plan must be approved quickly."
The president tweeted a second time, a few minutes later, saying his "thoughts and prayers" are with those in DuPont. He thanked the first responders to the accident.