NEW YORK (AP) -- Investigators looking into a deadly train derailment said Tuesday that no problems had been found with the train's brake system or track signals along its route and that its engineer was being questioned again.
The Metro-North Railroad commuter train was traveling Sunday at 82 mph as it approached a 30 mph zone and jumped the tracks along a sharp curve. Four passengers died.
The National Transportation Safety Board said investigators hadn't found any evidence of brake or signal trouble during the train's nine previous stops. NTSB member Earl Weener said Tuesday there were "no anomalies."
While investigators had yet to finish talking with engineer William Rockefeller, questions swirled around him because the train went into the curve at nearly three times the speed limit. Dozens of people were injured.
As NTSB worked to determine what caused the Sunday morning wreck in the Bronx, Gov. Andrew Cuomo said Rockefeller should be disciplined for "unjustifiable" speed.
Rockefeller stayed out of sight.
"This is a man who is totally distraught by the loss of life, and he's having a tough time dealing with that," said Anthony Bottalico, his union leader.
Weener said Monday that information from the data recorders indicates the throttle was let up and the brakes were fully applied just five or six seconds before the train came to a grinding, smoking halt.
Investigators said it was soon to say whether the excessive speed was the result of human error - say, a sleepy or distracted operator - or a mechanical problem.
Investigators began talking to the engineer Monday but didn't complete the interview.
The New York Police Department is conducting its own investigation, with help from the Bronx district attorney's office, in the event the derailment becomes a criminal case.
Whatever the findings on the cause of the crash, Cuomo said Tuesday the engineer could be faulted for the train's speed alone.
"Certainly, we want to make sure that that operator is disciplined in an appropriate way. There's such a gross deviation from the norm," he said.
An attorney for Rockefeller didn't immediately return calls Tuesday, but his union spoke up in his defense.
"Once the NTSB is done with their investigation and Billy is finished with his interview, it will be quite evident that there was no criminal intent with the operation of his train," Bottalico said.
Rockefeller, 46 and married with no children, has worked for the railroad for about 20 years and has been an engineer for 11, Bottalico said. Rockefeller lives in a well-kept house on a modest rural road in Germantown, N.Y., about 40 miles south of Albany.
He started as a custodian at Grand Central Terminal, then monitored the building's fire alarms and other systems, and ultimately became an engineer.
"He was a stellar employee. Unbelievable," said his former supervisor, Michael McLendon, who retired from the railroad about a year ago.
McLendon said he was stunned when he heard about the crash, shortly after opening his mail to find a Christmas card from Rockefeller and his wife.
"I said, `Well, I can't imagine Billy making a mistake,'" McLendon said. "Not intentionally, by any stretch of the imagination."
Rockefeller's work routine had recently changed. He had begun running that route on Nov. 17, two weeks before the wreck, said Marjorie Anders, a spokeswoman for Metro-North's parent, the Metropolitan Transportation Authority.
Bottalico said Rockefeller had changed work schedules - switching from afternoons to the day shift, which typically begins at 5 a.m. - but was familiar with the route and qualified to run it.
In case of an engineer becoming incapacitated, the train's front car was equipped with a "dead man's pedal" that must be depressed or else the train will automatically slow down, Anders said.