Investigators yet to question engineer over deadly New Jersey train crash
Investigators leading the probe into the deadly train crash at New Jersey's Hoboken station have held off questioning the engineer because of his injuries.
National Transportation Safety Board experts were also looking for clues from the train's black box recorders.
They want to know why the NJ Transit commuter train with engineer Thomas Gallagher at the controls smashed through a steel-and-concrete bumper and hurtled into the station's waiting area on Thursday morning.
A woman on the platform was killed, and more than 100 others were injured.
NTSB vice chairwoman T. Bella Dinh-Zarr said the board, the lead agency in the investigation, has been "in touch" with the injured engineer Mr Gallagher but has yet to interview him.
She said blood and urine were taken from him and sent for testing, standard procedure in train accidents.
However, a government official said that investigators from one of the other agencies taking part in the probe interviewed Mr Gallagher three times on Friday.
The official would not disclose what Mr Gallagher said but described him as co-operative.
Meanwhile, investigators retrieved the event recorder that was in the locomotive at the rear of the train but have not yet been able to download its data and have gone to the manufacturer for help, Ms Dinh-Zarr said. The event recorder contains speed and braking information.
The NTSB also has not been able to extract a recorder from the forward-facing video camera in the train's mangled first carriage.
Ms Dinh-Zarr said the wreckage cannot yet be safely entered because it is under a collapsed section of the station's roof.
Investigators were also reviewing security video from the railway station, setting out to inspect the nearby tracks, and gathering records on the crew members' training, scheduling and health.
The engineer, conductor and brakeman "have been very co-operative," she said.
Mr Gallagher, 48, a NJ Transit engineer for about 18 years, was pulled from the wreckage, treated at a hospital and released.
"The one thing we know for sure is that the train came into the station too fast. Why that is, we don't know," New Jersey Governor Chris Christie said.
"Was it error by the engineer? Did he have some type of medical emergency or circumstance that rendered him unable to control the train? Was there some equipment failure that didn't allow him to slow down?"
Some witnesses said they did not hear or feel the brakes being applied before the crash. The authorities would not estimate how fast the train was going before it hit the bumper at the end of its track, but the speed limit into the station is 10mph.
Falling debris from the crash killed 34-year-old Fabiola Bittar de Kroon, who had just dropped her toddler daughter off at day care before rushing to catch a train. Sixteen of the injured remained in hospital, two in intensive care.
More than 100,000 people use NJ Transit to commute from New Jersey to New York City each day. The NJ Transit portion of the Hoboken station remained closed on Friday, slowing the morning commute.
The crash has raised questions of whether technology called positive train control would have made a difference if NJ Transit had installed it.
The GPS-based system is designed to prevent accidents by automatically slowing or stopping trains that are going too fast.
Railroads are under government orders to install positive train control by the end of 2018. The deadline has been repeatedly extended at the industry's request.