The train that derailed over a major US highway was travelling 80-kilometres per hour above the speed limit at the time of the accident.

Investigations are continuing into the derailment of the Amtrak train, which plunged off a bridge and over a highway in the US state of Washington.

US Correspondent Zoe Daniel told Mike Hosking the train's black boxes appear to show speed is to blame.

"Initially reports suggest that the train didn't slow down as it should have to take that bend. The engineer did survive the crash and he will be interviewed."

LISTEN ABOVE AS ZOE DANIEL SPEAKS WITH MIKE HOSKING