The flames broke out after 11 p.m. Friday in the 500 block of 45th Street.
Firefighters arrived to find heavy fire on the second floor.
They rescued a 4-year-old child from the second floor and several other people from the top floor before gaining the upper hand.
FDNY Assistant Chief Michael Gala said a total of sixteen people were treated for injuries.
"An NYPD unit was on the scene, and as our members were bringing very quickly victims out to the street, our partners in the NYPD assisted us to get them expeditiously to nearby hospitals," said Gala.
Five people were taken to area hospitals with serious injuries, the FDNY said, including a 4-year-old child suffering from smoke inhalation and said to be in critical condition.
Fortunately, all of the injured are expected to survive.
No firefighters were injured.
The fire was out in about 45 minutes and only reached one alarm.
Meanwhile, family members returned to what was left of their home Saturday morning.
One of the residents say he had to make a split-second decision and jumped from a third-floor window with several others. He says all he could think about was escaping.
Neighbors who were also evacuated say a lot of children lived in the building.
"I feel very bad, the lady yesterday was sobbing 'I want to see my nieces,' sad to see," neighbor Maria Ventura said. "This is really sad, everyone's belongings burned, it's really unfortunate."
The FDNY returned to the scene Saturday with the fire marshals and investigators looking for a cause.
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