The New York City-bound train that derailed on Sunday, killing four passengers and injuring more than 60 others, was traveling at a speed of more than 82 mph around a 30 mph curve, the National Transportation Safety Board said Monday, according to Fox News.

Commuters were still feeling the impact of Sunday morning's derailed train in the Bronx on Monday, as transit was delayed while NTSB investigators were on the scene.

Those who died, as identified by the MTA Police Department and reported by Fox News, are Ahn Kisook, 35, of Queens; Donna L. Smith, 54, of Newburgh; James G. Lovell, 58, of Cold Spring, N.Y. and James M. Ferrari, 59, of Montrose, N.Y.

Commuters traveling into New York City were warned that delays should be expected as federal authorities began their investigation of the accident, which happened near the Spuyten Duyvil station on Metro-North's Hudson Line, according to Fox News. The eight-car train left Poughkeepsie just before 6 a.m. The train was scheduled to arrive at Grand Central Station at 7:43 a.m., but the train derailed around 7:22 a.m.

New York Governor Andrew Cuomo told news anchors of "The Today Show" Monday morning that speed could have been a factor. Cuomo said the National Transportation Board is looking into whether the accident was the operator's error, a problem with the track or an issue with the train.

As of Monday night, it was still unclear whether the alleged high speed was the operator's error. The train operator was tested for drugs and alcohol, although the results were not made available yet.

Seven cars of the train toppled over in the accident, Fox News reported, with the lead car left just inches from water. Construction crews are working with cranes to move pieces of the train that had been moved off track.

Transit between New York City and Albany was suspended on Sunday but had since been restored.