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A New York City subway train conductor was killed and at least 16 other people were hurt in an underground fire Friday morning, officials said.

More than 100 firefighters responded to the train blaze in Harlem, just above Central Park, at 3:18 a.m., New York City Fire Department Deputy Assistant Chief Fred Schaaf said during an early-morning news conference.

Police, fire marshals and federal agents with the Bureau of Alcohol, Tobacco, Firearms and Explosives were at the subway station at 110th Street and Central Park North on Friday investigating.

Authorities are treating the blaze as suspicious, and investigators were questioning an apparently emotionally disturbed person, two senior law enforcement officials told NBC New York. A statement from the Metropolitan Transportation Authority said it is offering an up to $50,000 for information leading to an arrest.

Among those hurt in the fire were four people who suffered life-threatening injuries and one with serious injuries, according to the fire department. In addition, 11 people, including four firefighters, sustained minor injuries.

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The conductor was identified by his union as Garrett Goble, 36. He died at a hospital.

Garrett Goble. TWU Local 100 / via Facebook

“This is a terrible tragedy ... a young man serving the public during a national crisis was killed at just 36 years of age," said Transport Workers Union Local 100 President Tony Utano in a statement. "This is a sad day for our entire City. We’re devastated.”

He said Goble had "acted heroically to move passengers to the platform out of danger."

"For this to happen, after we lost two of our union brothers to the Coronavirus, is hard to comprehend," Utano added. “These may be the darkest days that TWU Local 100 has gone through.

"We’ve been some tough times together. We’ve had more than our share of tragedies. This is different. We can’t grieve together. We can’t mourn together, at least not physically, as we have done in the past. But we remain a family," he said.

The MTA also said that Goble, and another conductor, helped passengers escape the train and the platform.

"Our colleague was a young man who had served the people of New York City at Transit for many years. The entire MTA family mourns his death alongside a grateful city," MTA Chairman and CEO Patrick J. Foye said in a statement.

Schaaf said heavy fire came from at least one train car, and that firefighters were met with challenging high-heat conditions. Two cars were quickly evacuated.

Large plumes of smoke could be seen billowing out of street grates near where the train halted. The fire had started at Broadway and 96th Street, police said.

The fire, which broke out in a northbound train, affected service through the morning and afternoon, according to the MTA. Far fewer commuters are using the subway system during the coronavirus pandemic, but the MTA has also greatly decreased the number of trains that are running.