On Sunday, the train was about half full, with about 150 people aboard, when it ran off the rails around 7:20 a.m. while rounding a bend where the Harlem and Hudson rivers meet. The lead car landed inches from the water. More than 60 people were injured.
The injured included five police officers who were heading to work, Mayor Michael Bloomberg said.
Gov. Andrew Cuomo said Monday the NTSB findings make it clear "extreme speed was a central cause" of the train derailment. He said his administration is working closely with the NTSB and when the investigation concludes he'll make sure "any responsible parties are held accountable."
The train was configured with its locomotive pushing from the back instead of pulling at the front. Weener said that's common and a train's brakes work the same way no matter where the locomotive is. Ditmeyer said the locomotive's location has virtually no effect on train safety.
The dead were identified as Donna L. Smith, 54, of Newburgh; James G. Lovell, 58, of Cold Spring; James M. Ferrari, 59, of Montrose; and Kisook Ahn, 35, of Queens.
Lovell, an audio technician who had worked the "Today" show and other NBC programs, was traveling to Manhattan to work on the Rockefeller Center Christmas tree, longtime friend Janet Barton said. The tree-lighting ceremony is Wednesday night.
"He always had a smile on his face and was quick to share a friendly greeting," ''Today" executive producer Don Nash said in a message to staffers.
The NTSB has been urging railroads for decades to install Positive Train Control technology. In 2008, Congress required dozens of railroads, including Metro-North, to do so by 2015.
The MTA awarded $428 million in contracts in September to develop the system for Metro-North and its sister Long Island Rail Road.
But the MTA has asked for an extension to 2018, saying it faces technological and other hurdles in installing such a system across more than 1,000 rail cars and 1,200 miles of track.
"This incident, if anything, heightens the importance of additional safety measures like that one," said U.S. Sen. Richard Blumenthal, of Connecticut, which is served by Metro-North. "I'd be very loath to be more flexible or grant more time."
MTA spokeswoman Margie Anders said the agency began planning for a PTC system as soon as the law was put into effect.
"It's not a simple, off-the-shelf solution," she said.
The derailment came amid a troubled year for Metro-North and marked the first time in the railroad's 31-year history that a passenger was killed in an accident.
In May, a train derailed in Bridgeport, Conn., and was struck by a train coming in the opposite direction, injuring 73 passengers, two engineers and a conductor. In July, a freight train full of garbage derailed near the site of Sunday's wreck.
Eltman reported from Mineola. Associated Press writers Kiley Armstrong, Verena Dobnik, Deepti Hajela, Ula Ilnytzky, Colleen Long, Jake Pearson and Jennifer Peltz contributed to this report.