US federal investigators have recovered one of the black box recorders from the wrecked commuter train at New Jersey's Hoboken station as inquiries continue into what caused it to crash, killing one person and injuring more than 100 others.
The two event recorders could contain information on the train's speed, braking and other conditions which can help investigators determine whether the tragedy resulted from an equipment malfunction or a distracted or incapacitated engineer.
The second box has been located but has not yet been recovered, though efforts are continuing.
Investigators from the US National Transportation Safety Board (NTSB) will be looking to determine how fast the train was going when it crashed at the busy station on Thursday morning. They also hope to speak to the train's injured engineer later.
The investigation will seek to find out whether a system designed to prevent accidents by overriding the engineer and automatically slowing or stopping trains which are going too fast could have helped if it had been installed on the line.
Authorities are struggling to extract a second recorder from the forward-facing camera on the train without damaging it, the NTSB said. That recorder should show what was ahead of the train before it crashed.
More than 100,000 people use New Jersey 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 for those making connections there.
As investigators began their probe, the family of Fabiola Bittar de Kroon, the crash's sole fatality, was in mourning.
Ms de Kroon had recently moved to New Jersey from Brazil after her husband got a job with an international liquor company.
She had just dropped her toddler daughter off at day care before rushing to catch a train, according to day care director Karlos Magner.
"We had a good talk for like a minute," he said. "She said she was in a rush."
Shortly after, the NJ Transit train ran off the end of the track as it was pulling in at around 8.45am, smashing through a concrete-and-steel bumper.
As it ground to a halt in the waiting area, it knocked out pillars, collapsing a section of the roof.
Ms de Kroon was killed by debris, and 108 others were injured, mostly on the train, New Jersey state governor Chris Christie said. Scores of people were taken to hospital, some with serious injuries including broken bones.
The engineer, Thomas Gallagher, was pulled from the mangled first car and was treated at a hospital and released. Mr Gallagher has worked for NJ Transit for 29 years, and a union roster shows he started as an engineer about 18 years ago.
The NTSB has been pressing for new safety technology for at least 40 years, and the industry is under government orders to install it, but regulators have repeatedly extended the deadline at rail firms' request. The target date is now the end of 2018.
Over the past 20 years, the NTSB has listed the lack of positive train control as a contributing factor in 25 crashes. Those include the Amtrak incident last year in Philadelphia in which a speeding train ran off the rails along a curve. Eight people were killed.
Tom Spina, a maintenance supervisor for a private company who was in the terminal at the time, described the scene: "It was chaotic. There was yelling and screaming, a lot of people in shock.
"Things like this we see in movies," he said. "You don't think you're going to see it in real life."