"We have recovered the event recorder of the cab car. We have downloaded the data off the locomotive. We've not had a chance to analyze it," said National Transportation Safety Board member Earl Weener.
The recorders may provide information on the speed of the train, how the brakes were applied and the throttle setting, according to Weener.
Investigators planned to conduct interviews Monday or Tuesday with the engineer and conductor. Officials briefed on the investigation told ABC News that the train's operator told emergency workers the brakes had failed. No problems have been found.
The engineer's cell phone has been confiscated by officials to examine call and text records. Officials tell ABC News that this is standard practice and that there is no indication that the operator did anything wrong at this point.
Anthony Bottalico, executive director of the Association of Commuter Rail Employees, said the Metro-North employee "is totally traumatized by everything that has happened." He said the engineer was "cooperating fully to get to root cause" of the wreck.
"He's a sincere human being with an impeccable record, that I know of. He's diligent and competent," said Bottalico.
In the wake of Sunday's deadly crash, NTSB officials worked overnight collective evidence. Spotlights were brought in to illuminate the wreckage.
The train was traveling from Poughkeepsie to Grand Central Station and carrying about 150 people when it derailed as it rounded a riverside curve entering the Spuyten Suyvil Station.
According to NTSB officials, preliminary information from event recorders indicate the train was traveling at approximately 82 mph as it entered the 30 mph curve. Seconds before the train stopped, the throttle idled and the brake pressure dropped to zero.
What investigators have not yet determined is why the train was traveling so fast.
Four people died of blunt force trauma and more than 60 people were injured including the engineer.
At least two of the train's cars flipped on their side during the crash, killing Donna L. Smith, 54, of Newburgh, N.Y., James G. Lovell, 58, of Cold Spring, N.Y., James M. Ferrari, 59, of Montrose, N.Y., and Ahn Kisook, 35, of Queens, N.Y.
One car allegedly stopped only feet from the banks of the Harlem River. Firefighters, rescue workers and ambulances responded quickly to the scene, and some firefighters broke through windows to remove passengers to the train.
The NTSB said its investigators could spend up to 10 days probing all aspects of the accident that toppled seven cars and the locomotive at a bend in the Bronx where Hudson and Harlem rivers meet. The speed limit on the curve is 30 mph, compared with 70 mph in the area approaching it, said Weener.
Of utmost concern to investigators is whether excessive speed, mechanical problems or human error played a role in the crash.
Workers began righting the toppled rail cars Monday as the 26,000 weekday riders of the affected line used shuttle buses and cars to get to work. But no major delays were reported during the early rush hour, railroad spokesman Aaron Donovan said.
ABC News and The Associated Press contributed to this report.