UPDATE: FDNY Releases Cause of Fire in Manhattan High-Rise Building

Two dozen people were injured in a high-rise building fire on Manhattan's West Side, including 17 civilians and four firefighters, one of whom suffered serious burns, fire officials say.

Among the injured civilians was a 7-year-old girl who was found in cardiac arrest on the 21st floor, according to FDNY Chief of Department James Leonard. Residents in the apartment performed CPR on her, reviving her, before firefighters carried her down the stairs and out of the building. She is now in good condition.

It's not clear what sparked the blaze inside a third-floor apartment at 515 West 59th St., near 10th Avenue, at about 5 p.m., but fire officials say the windows were left open and the heavy winds sent smoke into the hallways and up inside the building.

"Firefighters had a tough time getting across that hallway because of the wind," said Leonard, adding there was also "very heavy smoke" on the upper floors.

The 33-story building, which contains 465 apartments, is used as a residence building for Mt. Sinai Hospital, according to fire officials. Leonard said there were nine people who went to the roof to wait out the fire, and a police helicopter kept watch over them until they were safely removed from the building.

One resident named Josh said he had just left a nearby grocery store when he saw smoke billowing out from the building, where his sister was still in their 10th-floor apartment.

"She was inside, she was gonna get out, and all of a sudden she burned her hand on the railing as she was trying to hold onto it," he said.

One resident named Josh said he had just left a nearby grocery store when he saw smoke billowing out from the building, where his sister was still in their 10th-floor apartment.

"She was inside, she was gonna get out, and all of a sudden she burned her hand on the railing as she was trying to hold onto it," he said.

Of the 20 civilians who were hurt, six are in serious condition, the FDNY said on Twitter late Thursday night. Earlier, Leonard had said two civilians were in critical condition and four were in serious condition.

Firefighters have knocked out the fire, and were still making the final searches of the apartments in the building but they believe everyone has been accounted for.

Leonard reminded New Yorkers living in high-rise fireproof buildings of the importance of closing the door behind them while escaping their burning apartment, so that the wind does not feed the fire.

Residents who live in a fireproof building where another apartment -- not their own -- catches fire should generally stay inside, cover the doors with a towel and stay on the phone with 911.

"We do not want people out in the smoky hallways," Leonard said.

Those escaping fires in buildings should also never use elevators.