An MTA motorman was killed and 16 people injured when flames tore through a train in Harlem early Friday — and officials believe the blaze may be an arson tied to a spate of other subway fires that broke out along the line around the same time.

A person-of-interest was being questioned by police Friday afternoon, but had been released by early Saturday; no arrests have been made, law-enforcement sources told The Post.

Train operator Garrett Goble, 36, was found unconscious on the tracks at the 110th Street-Central Park North subway station by first responders amid the 3:15 a.m. two-alarm fire aboard a northbound No. 2 train, police said. It’s unclear how the worker ended up on the tracks.

He was rushed to Mount Sinai Hospital, where he was pronounced dead.

Goble, a married father of a 5-month-old baby and six-year MTA employee, was among the essential city workers who reported for duty during the coronavirus pandemic.

The MTA and NYPD were offering a combined $52,500 reward for information leading to an arrest.

TWU Local 100 President Tony Utano called the incident a “terrible tragedy,” adding, “This is a sad day for our entire city. We’re devastated.

“He was starting a whole new career,” Utano told reporters of Goble. “He was family, and now it’s over. It’s over just like that.”

The blaze — which erupted inside the second car of the train, leaving it completely charred and gutted — is suspicious and being investigated as a criminal matter, police said.

“As [the train] reached 110th Street here, an employee that was on the train reported to the motorman that there was heavy smoke and fire coming from the second car,” NYPD Deputy Chief Brian McGee, commanding officer of detectives at Manhattan North, told reporters at a press conference.

“The train stopped, and many people got off because there was a large, large fire on that train,” McGee said.

Sources said a shopping cart was found badly burned on the train — and police believe that the blaze may have started in the cart.

The MTA said that the train’s conductor and an additional conductor who was on board the train but off-duty helped straphangers flee to safety.

Utano said the No. 2 train’s conductor “is a little traumatized” but added, “He was happy that what he did to save the passengers made him feel that he did a good thing.”

Authorities said three men and one woman were taken to Mount Sinai Hospital for smoke inhalation, while five firefighters were taken to local hospitals with minor injuries.

Seven others were treated at the scene, police said.

Investigators were probing three other smaller fires that had been set on platforms also along the No. 2 line in Upper Manhattan — at 86th Street, 96th Street and 116th Street, McGee said, adding that all the fires started around the same time.

“I’m not saying that they are connected, but it’s something that we have to investigate,” he said.

Firefighters responded to reports of smoke at the 86th Street station at 3:05 a.m., the FDNY said. Details on the exact timing of the other fires were not immediately available.

Police were combing the train stations for surveillance footage, sources said.

MTA Chairman and CEO Patrick Foye said the MTA is offering $50,000 for information that leads to the arrest and conviction of the person or people “responsible for this tragedy.”

“The entire MTA family mourns [Goble’s] death alongside a grateful city,” Foye said. “Our hearts break for his family, loved ones and all those who knew him.”

The MTA and NYPD were offering a combined reward of up to $52,500 for information leading to the arrest and conviction of the person or people responsible for the fatal incident.

Additional reporting by Olivia Bensimon and Craig McCarthy