(NECN/NBC News: Jay Gray) - Investigators have located the "black box" in the wreckage of a New York commuter train.
Data from the box could help to explain how and why the train flew off the tracks, killing four and injuring dozens.
NTSB Board Member Earl Weener said, "Our mission is to understand not just what happened, but why it happened."
Passengers say they sensed there was a problem as the train rambled into a sharp turn.
Along the Harlem and Hudson Rivers, about 20 minutes from its final stop at Grand Central Station, the train went out of control and off the tracks, killing four and injuring more than 60.
One passenger said, "We were going fast. It hit the curve, it was flying!"
Passenger Dennis O'Neil said, "I hit the window and all the chairs came out and the woman who was sitting across the aisle came, you know, hit me."
Survivors described the moment of impact.
Passenger Sherill Patton said, "As we were going over, I looked over to my two friends, screamed and said, 'We're going over.'"
Local, state, and federal investigators, led by the National Transportation Safety Board, continue to pour over the scene.
Much of their focus is on the two cars on their sides, inches from the water.
The complete investigation is expected to take a week to 10 days.