Latest: Derailed Amtrak train 'travelling at 80mph in 30mph zone'; Three confirmed dead

A train making the first run along a faster new route hurtled off an overpass in the US and spilled some of its cars on to the road below, killing at least three people, authorities said.

Update 8.12am:The Amtrak train which derailed south of Seattle, killing three people and injuring dozens more, was travelling at 80mph in a 30mph zone, investigations have revealed.

The US National Transportation Safety Board (NTSB) said information from the event data recorder in the rear locomotive provided information about the train's speed at the time of the derailment in Washington state.