Preliminary data from the event recorders aboard the train clocked it at 82 mph as it approached the 30-mph curve, where the Hudson and Harlem rivers converge, in New York's Bronx borough, officials said Monday.
The data show the engineer cut the throttle and slammed on the brakes, but those moves came "very late in the game", National Transportation Safety Board member Earl Weener was quoted as saying by CNN.
"This is raw data off the event recorders, so it tells us what happened. It doesn't tell us why it happened," he said.
Investigators questioned the engineer, William Rockefeller, and the rest of the train crew Monday. Rockefeller told investigators he applied the brakes, but the train didn't slow down, the news channel said citing a law enforcement official.
But while the cause of the derailment has not yet been determined, investigators have seen no indication of brake problems, Weener said.
In a statement issued Monday evening, New York Governor Andrew Cuomo said the data "makes clear that, as we suspected, extreme speed was a central cause of this crash".
"The lives that were lost yesterday (Sunday) are a stark reminder that protecting the safety of all New Yorkers must be our top priority," Cuomo said.
"When the investigation concludes, we will make sure that any responsible parties are held accountable. My thoughts and prayers continue to be with the families of the victims of yesterday's (Sunday) crash."
The Hudson Line carried 15.9 million people last year. About 150 were aboard when the train derailed, authorities said.