The Amtrak train that veered off a bridge over a highway in the US state of Washington was travelling at more than twice the speed limit during its first run on a new route.
At least three people aboard the train were killed in the Monday morning (local time) accident in the city of DuPont, in which all 12 carriages and one of its two locomotives tumbled off the rails, officials said. Another 100 people were taken to hospitals, 10 with serious injuries.
The train was travelling on a new, slightly quicker route between Seattle and Portland, Oregon, with 86 people aboard, 80 of them passengers, Amtrak said.
It was speeding at 129km/h on a curved stretch of track where the speed limit was 48km/h, according to the National Transportation Safety Board. The board was investigating whether other factors besides speed were involved.
The wreckage and at least one towering crane glowed in the lights of scores of emergency vehicles in the wet, windy darkness early on Tuesday (local time) as workers sought to reopen the southbound lanes of the Interstate 5, a major West Coast highway stretching from the Canadian border to Mexico.
The accident placed Amtrak, the country's main passenger rail company, under renewed scrutiny following a series of fatal accidents.
The stretch of track where the derailment happened had previously been used by slow-moving freight trains but was recently upgraded to handle passenger trains as part of a US$181 million (NZ$259 million) project to cut travel time between Tacoma and Olympia.
Washington state's transportation department said the track underwent "weeks of inspection and testing" before the new route was inaugurated on Monday.