A train that derailed in New York City, killing four people and injuring dozens more, was travelling at 82mph as it approached a 30mph zone, officials have disclosed.
The Metro-North Railroad commuter train jumped the tracks on Sunday morning along a sharp curve where the speed limit drops from 70mph to 30mph.
Four people were killed and 60 others were injured when the train derailed on a riverside curve in the borough of the Bronx.
National Transportation Safety Board investigators today mined the train's data recorders, shedding light on such things as the train's speed and the use of its brakes.
Earl Weener, a board member of the National Transportation Safety Board, said investigators have already had some success in retrieving data, but the information has to be validated before it is made public.
Investigators plan to interview the engineer and conductor, Mr Weener said. He also said clues could be found from a signalling system operated by dispatchers at a central location.
The engineer, William Rockefeller, has been a Metro-North employee for about 20 years and an engineer for about 11, according to Anthony Bottalico, executive director of the Association of Commuter Rail Employees, the union representing all crew members.
Mr Bottalico said Mr Rockefeller, 46, "is totally traumatised by everything that has happened" and was "cooperating fully to get to root cause" of the wreck.
"He's a sincere human being with an impeccable record, that I know of. He's diligent and competent," Mr Bottalico said.
The train's assistant conductor, Maria Herbert, suffered an eye injury and a broken collarbone in the crash.
About 150 people were on board when the train derailed on Metro-North's Hudson line.
The NTSB said its investigators could spend up to 10 days probing all aspects of the accident that toppled seven cars and the locomotive.
New York Governor Andrew Cuomo said on NBC's Today show that he thinks speed was a factor. The governor, speaking from the crash site for a second day, said other possible factors ranged from equipment failure and operator failure to a track problem.
"It was actually much worse than it looked," Mr Cuomo said.
"As the cars were skidding across the ground, they were actually picking up a lot of debris, a lot of dirt and stones and tree limbs were going through the cars so it actually looked worse up close".