The train entered the Hoboken station “at a high rate of speed” and "crashed through the barriers, bringing it into the interior wall of the terminal, New Jersey Governor Chris Christie said.
A 34-year-old resident of Hoboken, who state medical examiners identified as Fabiola Bittar de Kroon, was standing on the platform when she was hit and killed by debris from the crash, Christie told CNN. She was the sole confirmed fatality.
The train’s engineer was treated at a local hospital before being released and was cooperating with an investigation into the crash, he said.
“We have no indication that this is anything but a tragic accident,” Christie said.
“Was it a system failure? Was it human error? Was it a medical emergency involving the engineer? We don't know.”
Video and photos on social media showed serious damage to the transit choke point just across the Hudson River from Manhattan, with the train tangled in wires and debris from what appeared to be caved-in portions of the roof.
The Hoboken terminal is a major transfer point for New Jersey trains and buses as well as ferries and the PATH commuter train that take passengers to New York.
Kenneth Garay, chief medical officer at Jersey City medical centre, said surgeons were “all hands on deck” treating patients with broken bones, internal injuries and lacerations.
“None at this point are life-threatening,” he said on CNN. “They’re critical and stable and being carefully monitored.”
A total of 114 people were injured, Christie told the station. Of those, 55 were treated by emergency responders, while another 22 were transported to hospitals and 37 were walk-ins.
He said he had been contacted by the White House and was working with federal, state and local authorities to “make sure this investigation is seamless and coordinated.”
Structural damage and the possible presence of asbestos had prevented investigators from accessing the train cars, Bella Dinh-Zarr, vice chairwoman of the National Transportation Safety Board, told reporters.
Investigators would spend seven to 10 days on site, she added, saying they hoped to find the train’s event recorder – which would contain information about speed and braking – later in the day.
Democratic presidential candidate Hillary Clinton said she “was terribly upset this morning.”
“It’s a horrible accident,” the former New York senator said at a campaign rally in Des Moines, Iowa. “I just want to send our thoughts and prayers.”
Donald Trump also expressed his sympathies with the victims on Twitter.
“My condolences to those involved in today’s horrible accident in NJ and my deepest gratitude to all of the amazing first responders,” the Republican candidate said.
Appearing alongside Christie was New York Governor Andrew Cuomo, who cancelled a trip to Israel for the funeral of former president Shimon Peres.
“These are difficult times over these past weeks and months, between terrorist attacks and natural disasters,” Cuomo said, referring to a recent string of bombings in New York and New Jersey.
Train 1614 was arriving from Spring Valley, New York when it struck the Hoboken terminal building around 8:45am (1245 GMT), the New Jersey Transit agency said in a statement.
Passengers described a scene of chaos with dazed and bloodied people making their way to safety.
“We crashed and the lights went out. A few people screamed,” Leon Offengenden told CNN.
“It was pretty chaotic,” he added. “And people just in shock and everybody has photos and cameras out and iPads. It was pretty intense.”
Passengers described the train – which was carrying around 250 people – ramming full speed into the bumper at the end of the track.
“We never slowed down,” Jim Finan, a commuter from New Jersey, told Fox News. “We ploughed, I mean, right through the bumper.”
Investigators will be looking for similarities to a 2011 PATH commuter train crash at Hoboken that injured several dozen people, Dinh-Zarr said.
Christie said engineers were examining the structural integrity of the Hoboken terminal, which underwent lengthy repairs after being hit during Superstorm Sandy in 2012.
The last major train crash in the United States took place in May 2015, when an Amtrak train linking Washington to New York derailed in Philadelphia, killing eight and injuring 200.
In December 2013, a New York suburban train derailed in the Bronx while travelling at several times the speed limit, leaving four people dead and more than 60 injured.