DUPONT, Wash. -- An Amtrak train derailed on an overpass in Washington state Monday morning, with some of the 14 train cars careening onto vehicles on a highway below. The crash left at least three people dead and roughly 100 injured, officials said, and authorities are still combing through the wreckage to find victims.

Authorities said the derailed train cars struck five motor vehicles and two semi-trucks on the highway. At this time, all southbound lanes of traffic remain closed on Interstate 5.

"Today's tragic incident in Pierce County is a serious and ongoing emergency," Washington Gov. Jay Inslee wrote in a statement. "Trudi and I are holding in our hearts everyone on board, and are praying for the many injured. They are our top priority, and I know first responders are doing everything to ensure everyone has the care they need."

First responders are treating the derailment as a mass casualty incident. Authorities have not yet provided details on injuries.

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"Emergency crews are on the scene and the Amtrak Management is responding," an Amtrak spokesperson said in a statement. "Some injuries are reported. Service between Seattle and Portland is suspended for the time being."

Amtrak train 501, which departed shortly before 8 a.m. local time from Tacoma, was part of a new high-speed service that launched Monday morning. The train is able to carry up to 250 people, but Amtrak said there were approximately 80 passengers, five Amtrak crew members and one technician from Talgo, the train car manufacturer, on board at the time.

Cars from an Amtrak train lay spilled onto Interstate 5 below as some train cars remain on the tracks above Monday, Dec. 18, 2017, in DuPont, Wash. Elaine Thompson / AP

The Cascades service from Seattle to Portland was supposed to be rated for a maximum speed of 79 mph for the section where it derailed in DuPont, according to passenger Chris Karnes. KIRO-TV reports the train was traveling at 81 mph moments before the derailment.

Karnes, who was on board the train when it derailed, said the emergency doors on the train were not functioning correctly after the crash and passengers had to kick out train windows to exit.

CBS News correspondent Kris Van Cleave reports the train tracks themselves are not owned by Amtrak; they're maintained by a freight railroad.

"The tracks, known as the Point Defiance Bypass, are owned by Sound Transit," the Washington State Department of Transportation wrote in a statement Monday. "The tracks were previously owned by BNSF and were used for occasional freight and military transport."

Motorist Greg Mukai, who witnessed the derailment from the highway, described the incident as "really scary stuff."

"We suddenly had to go from our 60 mph down to zero as fast as possible," Mukai said. "We were all avoiding one another to try and avoid a collision there. We saw smoke and the passenger train hanging from the overpass and on the freeway."

The cause of the derailment remains under investigation. An NTSB team is being sent from Washington, D.C., to investigate the incident.

Follow along with live updates below. All times are Eastern unless otherwise noted.

7:40 p.m.: About 100 injured in crash

Around 100 people were transported to local hospitals after the incident, Washington State Patrol spokesperson Brooke Bova said Monday evening. "We have some that are critically injured that were transported so at this time we haven't had any updates," she said of those injured.

6:50 p.m.: Official: At least 3 killed in crash

At least 3 people were killed when the high-speed Amtrak train derailed Monday morning, Joint Information Center spokesperson Sara Foster told CBS News.

6:29 p.m.: Amtrak: About 80 passengers on board

About 80 passengers were on board the train that derailed near DuPont, Washington, Amtrak said in a statement, along with five Amtrak crew and a Talgo technician. The figures had fluctuated a bit throughout the day.

Amtrak spokesperson Gay Banks Olson said the train was not filled to capacity and that Amtrak is "very grateful there weren't more people involved," The Associated Press reports.

3:40 p.m.: Amtrak CEO discusses Cascades Train 501 incident

Train 501 derailed at 7:33 a.m. PT, with some cars leaving an overpass to Interstate 5, Amtrak president and co-CEO Richard Anderson said on a conference call with reporters.

The train consisted of 14 cars -- 12 Talgo passenger cars, each containing 38 seats, which serviced business class, coach cars and bistro service -- and two locomotives.

"We had a very tragic event this morning," Anderson said. "On behalf of everyone at Amtrak, I want to express that we are deeply saddened by all that has happened today. Our very first concern is taking care of everyone on board. We will fully and completely and openly cooperate with the NTSB."

Asked if positive train control (PTC), a system designed to prevent train collisions, was activated at the time of the derailment, Anderson responded, "No."

Anderson said he was unable to provide an update on the number or nature of injuries sustained in the crash. Anyone seeking information related to the train derailment should call Amtrak at (800) 523-9101.

2:43 p.m.: NTSB provides updates on derailment



NTSB board member Bella Dinh-Zarr held a news conference in Washington, D.C. to provide updates about the ongoing investigation.

Asked about the death toll, she responded: "We leave that to the local authorities to report."

"We are aware of the fact this was called an inaugural run of this service, but we want to check and make sure what that exactly means and find out more information about that specifically," she told reporters.

"It's a little bit too early to know right now" whether the crash was speed-related, Dinh-Zarr said.

Twenty NTSB investigators are headed to the scene.

2:06 p.m.: Trump addresses derailment in speech



During his speech unveiling his administration's national security strategy, Mr. Trump commented on the Amtrak derailment.

"Let me begin by expressing our deepest sympathies and most heartfelt prayers for the victims of the train derailment in Washington state," Mr. Trump said from the Ronald Reagan Building in Washington, D.C. "We are closely monitoring the situation and coordinating with local authorities. It is all the more reason why we must start immediately fixing the infrastructure of the United States."

1:56 p.m.: President Trump responds to derailment

President Trump responded to Monday's train derailment on Twitter, saying the accident "shows more than ever why our soon to be submitted infrastructure plan must be approved quickly."

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! — Donald J. Trump (@realDonaldTrump) December 18, 2017

Mr. Trump sent a second tweet offering his "thoughts and prayers" to those affected by the derailment.

My thoughts and prayers are with everyone involved in the train accident in DuPont, Washington. Thank you to all of our wonderful First Responders who are on the scene. We are currently monitoring here at the White House. — Donald J. Trump (@realDonaldTrump) December 18, 2017

1:00 p.m.: Family reunification center

A family reunification center has been set up at DuPont City Hall, KIRO-TV reports.

Anyone with questions about friends or family who traveled on the derailed train should call (901) 523-9101.

12:35 p.m.: Train passengers, motorists hospitalized

CBS News correspondent Kris Van Cleave reports first responders have set up triage tents at the scene.

A spokesperson with St. Joseph's Medical Center says a total of 77 patients are being transported to hospitals in Pierce and Thurston counties. Four of the patients will be treated for severe injuries.

Patients will also be sent to St. Clare Hospital, St. Anthony Hospital, and Tacoma General Hospital.

11:58 a.m.: Fatalities confirmed

KIRO-TV reports the sheriff's office confirms fatalities among passengers on the train. The death toll has not been released at this time.

Multiple motorists were reported injured on the roadway; however, no fatalities among drivers have been reported at this time.