At least six people dead as Amtrak train derails on highway bridge in Washington state

Cars from an Amtrak train lay spilled onto Interstate 5 below alongside smashed vehicles as some train cars remain on the tracks. AP Photo/Elaine Thompson

At least six people died after a passenger train derailed on a bridge over a major road in Washington state on Monday, hitting cars below.

Seventy-seven people have been taken to hospital. The fatalities are all believed to have been those who were on the train.

Amtrak, which provides intercity rail service in the US, said there were about 78 passengers and five crew aboard at the time.

Passenger Chris Karnes told local news outlet KIRO 7 that passengers were forced to kick out train windows to escape because emergency doors were not working properly after the derailment.

"We had just passed the city of DuPont and it seemed like we were going around a curve," Mr Karnes said. "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," he added.

The derailment occurred on the first day that Amtrak trains began using a new track between the cities of Tacoma and Olympia, part of a project to reduce travel time.

The new route takes trains along Interstate 5, eliminating a major choke point for passenger trains in Tacoma and allowing trains to reach speeds of 127kph, the state transport department has said.

It was not immediately clear whether the derailment, which came during a busy travel time one week before the Christmas holiday, was connected to the new route.

President Donald Trump dedicated a statement to the victims ahead of his speech on the US security strategy.

He tweeted to compared how far behind the US is in comparison to the investment the Middle East has spent on infrastructure.

Amtrak confirmed its train was involved and said "some injuries" had been reported but did not immediately offer further details.

The train derailed about7.30am in DuPont. A photograph posted by a Washington state police spokeswoman showed an upside-down train car partially crushed on the motorway, with a second car dangling off the overpass.

Authorities warned drivers to avoid the area.

The national transport safety board said on Twitter that it was gathering information about the incident.

"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," Washington governor Jay Inslee tweeted.