The blaze broke out around 6:30 p.m. in a third-floor apartment on East 118th Street near First Avenue.
Dozens of people are out of their homes and a 2-month old boy was seriously injured when the flames ripped through his family's apartment.
The infant was rushed to Harlem Hospital to be treated for smoke inhalation. He is listed in critical condition.
Five others were hurt, including four firefighters who were taken to St. Luke's Hospital for minor injuries.
More than 100 firefighters responded to the fire, which quickly made its way to the upper floors. It took about an hour and a half to get the flames under control.
One resident described the explosions and the intense heat that forced him out of the building.
"I heard the windows cracking and things just popping, just the flames was just very enormous and very big," Juan Irizarry said. "I just feared for my life."
The Red Cross is assisting 48 residents who were left temporarily homeless.
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