- 21 updates
A New York commuter train that derailed, killing four people, was travelling nearly three times faster than the speed limit, officials said.
The seven-carriage train had been travelling at 82mph before entering a 30mph speed limit zone on a curved section of the track where it crashed.
The train's brakes were working but they were applied "very late in the game", National Transportation Safety Board member Earl Weener told reporters.
He added that investigators were considering a driver error being the cause of the crash but had not yet ruled out other possibilities.
The four people killed as a train derailed in the Bronx area of New York City have been named, NBC News reports.
Jim Lovell, 58, James Ferrari, 59, Donna Smith, 54, and Ahn Kisook, 35, were killed when seven carriages flipped onto their sides after the train hurtled around a sharp curve.
Passengers were tossed around like rag dolls during the crash, authorities said.
A federal investigator says there is indication of a link between today's New York commuter train derailment and the derailment of a freight train that occurred in the same location in July.
"We will be looking at that, but at this point, we have no indication that it's a factor," National Transportation Safety Board member Earl Weener said.
Mr Weener said investigators would be on the scene of the crash in the New York city borough of the Bronx for seven to 10 days.
The Governor of New York, Andrew Cuomo, has told CNN that the site where the North-West train derailed was "a dangerous area on the track just by design".
Four people are confirmed dead after a train derailed near a sharp bend in New York this morning.
ITV News correspondent Richard Pallot reports.
Passengers on the North-West train which derailed in New York, killing at least four, have told how they thought they were travelling "a lot faster" than usual prior to its crash.
"It was coming towards Spuyten Duyvil and you could feel it starting to lean and it was like 'hey what's going on, and then it hit the curb real hard and flopped over and slid down the hill," Dennis O'Neil told NBC.
Passenger Frank Tatulli, who was in the first car, told television station WABC the train was travelling much faster than usual.
"The guy was going real fast on the turns and I just didn't know why because we were making good time," he said.
"And all of a sudden we derailed on the turn."
President Barack Obama says his thoughts and prayers are with the friends and families of the victims of New York City commuter train derailment.
The White House said the President will continue to stay in touch with New York officials throughout the day.
Helicopter footage from NBC News shows the train sprawled across the tracks on one bank of the Hudson River in the north of New York City:
New York City Fire Commissioner Salvatore Joseph Cassano has said if the New York commuter train had derailed on a workday and was at full occupancy, the result would have a been "tremendous disaster".
New York State's Metropolitan Transportation Authority said the train was about half full, with approximately 150 passengers on board at the time of the crash.
Three of the victims of the Metro-North train derailment were "ejected from the train", according to ABC News.
New York Governor Andrew Cuomo said the "train's operator had survived the crash" and was receiving treatment for "unspecified injuries".