Police say a 30-year-old male is being questioned after he was seen lurking around the scene of the fire, however, no charges have been filed.
The fire broke out inside the East 95th Street building just before 4:55 a.m. Tuesday.
Two people jumped from the second floor to escape the flames and were found by firefighters
One resident died and another was seriously injured.
Five others, including a firefighter, were also being treated for less serious injuries.
They went to Brookdale University Hospital and Kings County Hospital.
About 20 residents were displaced in the fire.
The door to the fire apartment was left open, allowing the flames to spread.
The cause is under investigation -- arson is being investigated as a possible cause.
ALSO READ | Family of 24-year-old who fell to death during NYC rooftop party speaks out
* More Brooklyn news
* Send us a news tip
* Download the abc7NY app for breaking news alerts
* Follow us on YouTube