New York: Dramatic videos circulating on social media showed flames engulfing the upper floors of a high-rise apartment building in the Bronx early Saturday, as firefighters battled a major blaze that spread across the top levels of the tower.

Footage shared online captured thick black smoke billowing from the building while flames ripped through several apartments. In some clips, residents were seen leaning out of windows, apparently trying to escape smoke-filled interiors, as emergency lights flashed below and responders worked to secure the area. Reports on social media suggested the fire may have followed an explosion, though officials have not confirmed this.

Firefighters battled the blaze on the top two floors of the high-rise, according to fire officials.

The 4-alarm fire in the Bronx started shortly after midnight and spread to multiple apartments in the 17-storey building, according to a statement from the New York City Fire Department.

There was no immediate word on what caused the fire.

More than 200 fire and emergency crews were working at the scene, according to the fire department.

It was not immediately clear if anyone had been injured.

Separately, AZ Intel reported that the incident may have been caused by a gas explosion, though authorities have yet to confirm the cause or any casualty figures.