An investigation is underway into what caused a New York commuter train en route to Manhattan to come off the tracks early Sunday, leaving four people dead and more than 60 injured.

The Metro-North Railroad passenger train derailed in the Bronx as it was coming around a sharp curve shortly after 7 a.m. Some of the rail cars flipped over.

Investigators with the U.S. National Transportation Safety Board are looking for 鈥渁ny anomalies鈥� that may have caused the derailment and will be examining speed, braking, track condition, train crew performance and 鈥渁ny possible data recorded by the signaling system,鈥� NTSB board member Earl Weener told reporters at the scene Sunday evening.

鈥淥ur mission is to understand not just what happened, but why it happened, with the intent of preventing it from happening again,鈥� Weener said.

Three of the dead were thrown "as the train came off the track and was twisting and turning," New York Fire Department Chief Edward Kilduff said.

He added that rescue crews had to use air bags under the train to remove some of the critically injured passengers. Others inside the train had to be cut from restraints.

The Metropolitan Transit Authority identified the four people killed Sunday:

  • Donna L. Smith, 54
  • James G. Lovell, 58
  • James M. Ferrari, 59
  • Ahn Kisook, 35

"Four people lost their lives today in the holiday season, right after Thanksgiving," New York Gov. Andrew Cuomo said at a news conference.

He asked that all New Yorkers 鈥渞emember them in your prayers tonight.鈥�

Of the dozens of passengers taken to area hospitals, officials said 11 of the injured are believed to be in critical condition, and another six are seriously injured. The train operator was among those injured, Cuomo said.

"It's obviously a very tragic situation. The first order of business is to care for the people who were on the train," Cuomo said.

A crane was en route to the scene Sunday evening to right the locomotive.

Cuomo didn't speculate on what could have caused the derailment.

鈥淎ny lessons from this tragedy are what we want to know and that鈥檚 basically the purpose of the NTSB鈥檚 investigation on site,鈥� he said at a later news conference.

The train was about 100 metres north of Spuyten Duyvil station when it came off the tracks close to where the Harlem and Hudson Rivers meet. None of the cars entered the water, but one ended up just metres from the edge.

The train left Poughkeepsie shortly before 6 a.m. Sunday morning and was expected to arrive at Grand Central Terminal at approximately 7:45 a.m.

Officials said between 100 and 150 people were on the train at the time of the crash.

Joel Zaritsky told The Associated Press he was on his way to New York City for a dental convention when the accident occurred.

"I was asleep and I woke up when the car started rolling several times. Then I saw the gravel coming at me, and I heard people screaming. There was smoke everywhere and debris. People were thrown to the other side of the train," he said, holding his bloodied right hand.

Passengers were taken off the derailed train, dozens of them bloodied and scratched, holding ice packs to their heads. The fire department said 130 firefighters responded to the scene.

U.S. President Barack Obama said his thoughts and prayers are with the friends and families of the victims of the train derailment. The White House issued a statement saying the president was briefed on the accident Sunday morning, and would continue to stay in touch with New York officials throughout the day.

Sunday's accident is the second Metro-North passenger train derailment in six months.

On May 17, an eastbound train derailed in Bridgeport, Connecticut, and was struck by a westbound train. The crash injured 73 passengers, two engineers and a conductor.

With files from The Associated Press