Victims with a spinal cord injury, an open leg fracture and other broken bones were being treated at St. Barnabas Hospital in the Bronx, one of the medical facilities that took patients, spokesman Steven Clark said.
Edwin Valero was in an apartment building above the accident. At first, he said, he didn't notice that the train had flipped over.
"I didn't realize it had been turned over until I saw a firefighter walking on the window," he said.
To Cuomo, "it looked like a toy train set that was mangled by some super-powerful force," the governor said in a phone interview with CNN.
As deadly as the derailment was, the toll could have been far greater had it happened on a weekday, or had the lead car plunged into the water instead of coming to rest on its edge.
"On a workday, fully occupied, it would have been a tremendous disaster," New York City Fire Commissioner Salvatore Joseph Cassano told reporters at the scene.
Amtrak Empire service was halted for hours between New York City and Albany but resumed Sunday afternoon, with some delays. Amtrak said its Northeast Corridor service between Boston and Washington was unaffected.
It was not clear when service would resume on the affected part of Metro-North's Hudson line, which carries about 18,000 people on an average weekday morning.
Westchester County Executive Rob Astorino said contingency plans were in the works for Monday morning rush hour, possibly using buses.
Sunday's accident was the second passenger train derailment in six months for Metro-North.
On May 17, an eastbound train derailed in Bridgeport, Conn., and was struck by a westbound train. The crash injured 73 passengers, two engineers and a conductor. Eleven days later, track foreman Robert Luden was struck and killed by a train in West Haven, Conn.
In July, a freight train full of garbage derailed on the same Metro-North line near the site of Sunday's wreckage.
"Safety is clearly a problem on this stretch of track," state Sen. Jeff Klein, who represents the nearby area, said Sunday.
Earlier this month, Metro-North's chief engineer, Robert Puciloski, told members of the NTSB investigating the May derailment and Luden's death that the railroad is "behind in several areas," including a five-year schedule of cyclical maintenance that had not been conducted in the area of the Bridgeport derailment since 2005.
The NTSB issued an urgent recommendation to Metro-North that it use "redundant protection," such as a procedure known as "shunting" in which crews attach a device to the rail in a work zone alerting the dispatcher to inform approaching trains to stop.
Associated Press writers Kiley Armstrong, Colleen Long, Jake Pearson and Jennifer Peltz in New York, Joan Lowy in Washington and Stephen Singer in Hartford, Conn., contributed to this report.
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