NEW YORK (CNN) -- A New Jersey Transit train plowed through a major station in Hoboken during Thursday morning's rush-hour commute, killing at least one person and injuring more than 100 others, some seriously, local officials said.
Active rescue operations remained underway more than two hours after the crash occurred.
Images posted on social media showed severe structural damage at the terminal -- one of the busiest transit hubs in the New York metropolitan area -- and part of the roof appeared to have collapsed.
An NJ Transit worker who was at the station said he heard an "explosion"-like sound as the lead car, coming into the station fast, slammed into a bumper block.
"It went up and over the bumper block, through the depot, and came to rest at the wall by the waiting room," the worker, Mike Larson, said.
Larson said the first car of the train hit with such force that it went airborne into the passenger concourse, Larson said. Half of the first car was crumpled and the roof crushed down to the seats, he said.
"I can't even begin to tell you how many people may be trapped in that first car."
The train's engineer was removed, unresponsive, from the train after the crash, an official assisting with rescue operation and briefed on developments, told CNN.
The National Transportation Safety Board has launched an investigation into the cause of the crash.
'I guess it didn't slow down'
A passenger, Leon Offengenden, said he was in one of the cars behind the lead car when the crash happened.
"The front car is essentially off the rails ... into the building of the station, with the roof sort of collapsed around it," he said.
"The first car was just demolished. The train looked like it went through the stop," Offengenden said. "The first car looked like it catapulted onto the platform into the building. The roof collapsed; there was wire and water everything. I'm just glad I wasn't in the first car and I'm alive."
Larson, the transit worker, said he didn't know how fast the train was going into the station, but it "was definitely faster than it should have been."
"The lights went out and a few people screamed (when the crash happened)," Offengenden said.
"I was sitting but I couldn't see the window. I didn't notice that the train was going at an accelerated pace. It was just going.
"Now, looking back, I guess it didn't slow down. It definitely didn't slow down. There was no brakes. All of a sudden, it just crashed. Something happened obviously. ... It's the same feeling as when you get in a car crash."
He said the train's conductor "told everyone there was a crash, and said if you're hurt, stay in the train."
"I got off and looked at the train and ... saw a man who had blood just running down his arm. He was wearing a suit and blood was just gushing."
An urban search-and-rescue team has been deployed and will assist in shoring up the structure and helping to remove people from the train, an emergency responder monitoring the situation said.
'It kept going and going'
Another passenger, Bhagyesh Shah, said he was riding in the back of the front passenger car on his way to work. Like Offengenden, he said the train didn't slow as it approached the station.
"The next thing I know, I'm on the floor. We are plowing through something ... and when the train came to a stop, I could see the parts of the roof on the first car and some of the debris next to me," Shah said.
People were thrown around, he said.
"I was hoping the train would stop now but it just didn't stop. It kept going and going. At the end of it, it felt like eternity."
He also saw people injured.
"There was a woman ... she was pinned under ... debris next to the first car. There were seven to eight people that tried to pick that (debris) up."
"I saw an old man, too, who had head injuries, trying to get out of the first car."
Rail service suspended
Rail service has been suspended in and out of Hoboken as a result of the crash, which happened on a cool day with overcast skies. The hub primarily serves the lower Manhattan commuter market.
CNN producer Paul Murphy described a chaotic scene, with the arrival of first-responders from various New Jersey agencies, sirens blaring and nearby streets cordoned off.
"The main sound you hear now are sirens -- sirens everywhere."
"There's only one option for people who don't have a car to get out of Hoboken right now, and that's the bus," Murphy said. "The bus lines are very, very long and many people are on the phones with work, saying, 'I'm not coming into work today or I'm going to work from home.'"
NJ Transit is the "third largest provider of bus, rail and light rail transit in the nation." Roughly 15,100 people board through the Hoboken station each weekday, according to the agency.
State officials have taken recent steps to improve rail safety.
In August this year, Gov. Chris Christie signed a bill prohibiting an engineer from operating a New Jersey Transit train if their driving privileges are suspended or revoked due to a conviction for driving under the influence of alcohol or drugs or a related offense.