The four-alarm fire broke out around 6:15 p.m at 23 W. 76th St. It spread between the second and sixth floors in the six-story residential building.
The New York City Fire Department sent 170 firefighters and 39 units to the scene.
Eight firefighters sustained minor injuries at the scene.
The normally quiet block became a smoky scene Thursday night. Firefighters took over as evacuees huddled together and hoped for the best.
"I said it smells like a fire like somebody's burning wood," said Monica, a tenant.
Tony and Monica were in their apartment at 23 West 76th Street.
"Within 5 minutes a neighbor pounded on the door. We opened up the door and we saw the smoke," Monica said.
They grabbed their cats and ran.
"This is a classic combustible building," a firefighter said.
Fire fighters say it started in a wall of a second floor apartment that's under construction.
And while flames never showed themselves, they quickly chewed through the guts of the building, travelling through the walls and pipes all the way to the top floor.
"Basically we chased it throughout the entire fire," a firefighter said.
Eventually the fire reached four alarms before firefighters declared it under control.
"That place has been questionable since they started six months ago," said Joseph Bolanos, block association president.
The investigation has only just gotten underway, but the block association president Joseph Bolanos blames the ongoing construction which he says has been dangerous and shoddy from the start.
That will be up to fire marshals and building inspectors to figure out. But for now, dozens of families are homeless.
"It's very scary because your whole life is in your apartment," Monica said.
Including Tony and Monica, who may have their cats but not much else.
"I had vintage guitars from '74. Gone. Unreplaceable," Tony said, "The rest I don't care about, the rest is Ikea. Who cares?"
The Red Cross is providing assistance to the displaced families.