- NEW: Fire chief: Three of the dead were thrown from the train
- At least four killed, dozens injured, officials say
- Train operator told investigators he applied brakes but they didn't work, source says
- The passenger train derailment occurred at a station in the Bronx
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New York (CNN) -- A passenger train derailment Sunday morning killed at least four people and injured dozens more, officials said.
Firefighters and emergency rescuers swarmed the scene near Spuyten Duyvil station in the Bronx, where at least two train cars had flipped on their sides. One car was just feet away from the Harlem River.
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 told reporters.
Police divers were in the water hours after the crash searching for survivors, and cadaver dogs combed the wreckage. Authorities believe all the passengers have been accounted for, New York Gov. Andrew Cuomo told reporters.
It was unclear how fast the train was traveling and how many passengers were on board.
At least 67 people were injured, New York Police Chief Ray Kelly told reporters.
"In terms of causes, we don't know exactly what happened," Cuomo said.
Federal investigators from the National Transportation Safety Board were headed to the scene, he said.
Cuomo said 11 people were critically injured.
The train had been traveling from the Hudson Valley town of Poughkeepsie, 100 miles north of New York, to New York's Grand Central Station.
It came off the tracks just as it was coming around a sharp curve shortly after 7 a.m., fire officials told CNN affiliate WCBS.
Of eight train cars, seven were off the tracks.
The train operator -- who is among the injured -- told investigators he applied brakes to the train, but it didn't slow down, a law enforcement official on the scene and familiar with the investigation said.
Passenger Frank Tatulli told WABC he thought the train was traveling "a lot faster" than usual.
He escaped a derailed car on his own and suffered head and neck injuries, he said. Other passengers were still on the train, he told WABC.
The derailment occurred near where a freight train derailed in July, WCBS reported. No one was injured in that accident.
Federal authorities are still investigating a collision that occurred on the same line in May, when two passenger trains crashed during rush hour in Connecticut.
Service was suspended Sunday on part of the Hudson Line, Metro-North said on Twitter.
Amtrak said it was suspending service between New York and Albany indefinitely after the derailment.