uomo said the investigation will focus on “why the operator didn’t stop the train before it hit the bumping block.”

“What happened with the operator, we don’t know,” Cuomo said. “Obviously there will be an investigation to find out.”

Kevin Sexton, general chairman of the Brotherhood of Locomotive Engineers and Trainmen Division 269, which represents 400 Long Island Rail Road engineers, did not immediately respond to a request for comment.

Robert Halstead, a Syracuse-based railroad accident reconstruction expert and investigator, said he expects the probe will focus on the train’s engineer — including any possible distractions, like personal electronic devices, and whether he was fatigued.

“They have to really look at the last 72 hours — see what his sleep-rest cycles were, when he went off-duty last time — to see if there’s any potential issue there,” Halstead said.

Atlantic Terminal features a “head house” configuration, where train tracks terminate facing a station building. Halstead said that while there is nothing inherently dangerous about the layout, “it does rely on human factor to successfully complete that movement.”

It’s a similar design to NJ Transit’s Hoboken station where in late September a train that failed to stop at the station crashed through concrete bumper blocks at the end of the line, killing one person and injuring more than 100.

Investigators in that accident later determined that the engineer had undiagnosed sleep apnea, which federal railroad officials have said could increase the risk of train accidents caused by engineer fatigue. The LIRR began testing engineers for the sleep disorder last year.

Despite the similar circumstances of the two accidents, Cuomo said the LIRR crash “is minor compared to what happened in Hoboken.”

“All things considered, this was a relatively minor accident,” Cuomo said.

In fact, MTA officials said they did not expect the accident to impact service, including during the evening rush.

Moriches railroad safety expert Carl Berkowitz agreed that investigators will likely key in on human error in the accident, which he said was likely made worse by the fact that many Brooklyn LIRR commuters move to the front of trains to more easily access connecting subway lines, and would have been standing as the train approached the end of its run.

“And a body in motion stays in motion,” said Berkowitz, who expects that many riders would have been violently thrown as the train came to a sudden stop.

Images on social media showed several emergency responders at the scene treating people for injuries, including some on stretchers.

“We started feeling the train jump the rail,” passenger Daniela Roth of Valley Stream said. “Then we heard the metal screeching and it felt like it was forever. And then we saw the smoke.”

“We were catapulted. Anyone who was standing fell,” she said.

Passenger Rob Schroeder of Woodmere said he was in the fifth car of the train and there was “not too much damage there.”

“I was sitting, so I was fine. I saw a couple of people who were standing that got tossed forward. One woman fell, but was OK,” he said.

Shortly after the accident, the railroad posted a message on Twitter: “Anticipate possible delays into and out of Atlantic Terminal this morning due to an incident at the terminal.”

Twitter users posted on the social media site about the accident Wednesday morning.

One of them, Ry Karl, posted a short video showing a damaged station door and passengers crowded around the platform.

“Well this is one way to start the morning,” Karl posted. My train crashed through Atlantic Terminal. Hope everyone else is OK.”

Atlantic Terminal is the LIRR’s second-busiest western terminal, behind Penn Station. It carries about 10,000 customers on an average weekday morning. Ridership on the line has surged in recent years, in part because of the development of the Barclays Center, which was built on a former LIRR rail yard across the street from the terminal.

The crash marks the second LIRR accident with injuries in less than three months. In October, an LIRR train derailed near New Hyde Park, injuring more than 30 people.

Mark Epstein, chairman of the LIRR Commuter Council — the railroad’s official watchdog group — said in a statement that while he was thankful that the injuries were not more serious the number of LIRR accidents in recent years is “troubling.”

Epstein noted that positive train control — the federally required crash prevention technology that the LIRR expects to have up and running by the end of 2018 — likely would not be active at a train terminal. He encouraged the LIRR to look at other “measures, technologies, and systems to reduce the risks of injury resulting from terminal collisions.”

“Ensuring safe operation must be the top priority of the LIRR, and we urge the Rail Road to do all that is possible to further the investigation of this incident and make its results available and apply them to enhance the safety of passengers and crew members.”