A team of investigators has been sent to the site of an Amtrak derailment in Montana in which three people died and seven people were hospitalised, officials have said.
The westbound Empire Builder was travelling to Seattle from Chicago when it left the tracks at about 4pm on Saturday near the small town of Joplin.
The train was carrying about 141 passengers and 16 crew members and had two locomotives and 10 cars, eight of which derailed, Amtrak spokesman Jason Abrams said.
A 14-member National Transportation Safety Board (NTSB) team including investigators and specialists in railroad signals were looking into the cause of the derailment on a BNSF Railway main track that involved no other trains or equipment, board spokesman Eric Weiss said.
The accident scene is about 30 miles (48km) from the Canadian border.
Most of the people on the train were treated and released for their injuries, but five people who were more seriously hurt remained at the Benefis Health System hospital in Great Falls, Montana, according to Sarah Robbin, Liberty County emergency services co-ordinator.
Another two people were at Logan Health, a hospital in Kalispell, Montana, spokeswoman Melody Sharpton said.
Liberty County Sheriff Nick Erickson said the names of the dead would not be released until relatives had been notified.
Ms Robbin said nearby residents had rushed to help when the derailment occurred.
“We are so fortunate to live where we do, where neighbours help neighbours,” she said.
Amtrak said it had sent emergency personnel and other officials to the site to help passengers, employees and local officials. It said company officials had been “deeply saddened” to learn of the deaths.
Following the derailment, Sunday’s westbound Empire Builder from Chicago was terminating in Minneapolis, and the eastbound train was originating in Minneapolis.
Passenger Megan Vandervest told The New York Times she had been woken by the derailment.
“My first thought was that we were derailing because, to be honest, I have anxiety and I had heard stories about trains derailing,” Ms Vandervest, from Minneapolis, said.
“My second thought was that’s crazy. We wouldn’t be derailing. Like, that doesn’t happen.”
She told the newspaper that the car behind hers was tilted, the one behind that was tipped over, and the three cars behind that “had completely fallen off the tracks and were detached from the train”.
Speaking from the Liberty County Senior Centre, where some passengers were being taken, Ms Vandervest said it had felt like “extreme turbulence on a plane”.
Residents of communities near the crash site quickly mobilised to help.
Chester councillor Rachel Ghekiere said she and others had helped about 50 to 60 passengers who were taken to a school.
“I went to the school and assisted with water, food, wiping dirt off faces,” she said.
“They appeared to be tired, shaken but happy that they were where they were. Some looked more dishevelled than others, depending where they were on the train.”
Allan Zarembski, director of the University of Delaware’s Railway Engineering and Safety Programme, said he did not want to speculate but suspected that the derailment stemmed from an issue with the train track or equipment, or a combination of both.
Railways had “virtually eliminated” major derailments by human error after the implementation of positive train control nationwide, Mr Zarembski said.
“I would be surprised if this was a human-factor derailment,” he said.
NTSB findings could take months, he added.
Bob Chipkevich, who oversaw railway crash investigations for several years at the NTSB, said the agency would not rule out human error or any other potential causes for now.
“There are still human performance issues examined by NTSB to be sure that people doing the work are qualified and rested and doing it properly,” Mr Chipkevich said.
Mr Chipkevich said track conditions had historically been a significant cause of train accidents. He noted that most of the track that Amtrak used was owned by freight railways and depended on those companies for safety maintenance.
