A New York commuter train that derailed Sunday morning, killing four passengers and injuring 67 others, was traveling nearly three times the posted speed limit at the time of the accident, says federal safety officials.

According to black-box recorder data gathered by the National Transportation Safety Board, the seven-car Metro-North train was traveling at 82 miles per hour when it entered a curve in the tracks with a 30 mile per hour speed limit near the convergence of the Hudson and Harlem rivers.

The derailment took place just after 7 a.m. on Metro’s Hudson line, 10 miles north of the train’s destination, Grand Central Station.

In the aftermath of the accident, the train’s conductor, William Rockefeller, told investigators that he had applied the brakes and that they had failed, however data collected has revealed that the brakes were working properly, and that they were applied only moments before the crash occurred.

“We do know that two minutes before the curve the train was going at 60 miles per hour and had accelerated then up to 82 miles per hour prior to entering the curve,” said NTSB member Earl Weener, also noting that the train’s brakes were activated just five seconds before the train left the tracks. “At this point we are not aware of any problems or anomalies with the brakes.”

When asked if the derailment was a result of operator error, Weener said, “At this point in time, we can’t tell.”

Rockefeller, who was hospitalized in the accident, is scheduled for questioning with the NTSB on Wednesday. The train operator was tested for drugs and alcohol immediately after the crash, though results have not yet been provided to federal investigators. As a standard investigation procedure, his cell phone was also taken away.

Anthony Bottalico, General Chairman of the Association of Commuter Rail Employees, has released a statement saying that Rockefeller has “never been disciplined on his job on the railroad,” and that “he is very traumatized. He’s devastated by the loss of life, by the injuries to the passengers and his fellow crew members, and he’s extremely upset about all of it.”

Following the release of the train’s black-box data, New York Governor Andrew Cuomo also released a statement saying that the data “makes clear that, as we suspected, extreme speed was a central cause of this crash… The lives that were lost yesterday are a stark reminder that protecting the safety of all New Yorkers must be our top priority. 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 crash.”