A massive fire swept through a vacant Chelsea building under renovation as a luxury condo complex early Tuesday – displacing terrified neighbors in the predawn hours amid fears of a collapse, officials said.

About 250 firefighters battled the five-alarm blaze, which erupted about 3 a.m. in the six-story building at 221 W. 17th St. and quickly spread to the upper floors and roof.

“Upon arrival, we had heavy fire on the top three floors of the building,” FDNY Chief of Department James Leonard said. “At this time, the building is in major danger of collapse, so we are keeping everyone away from the building.”

Among the residents evacuated from nearby buildings was acclaimed jazz musician Wynton Marsalis. He ran out with a horn in his hand, 1010 Wins reported — but was apparently upset because the fire disrupted his newspaper delivery.

“He loves his New York Post,” said J. K. Miller, who identified himself as the musician’s “in-house counsel.” “He later said, ‘Where’s my Post?'”

The cause of the fire, which was declared under control at 7:11 a.m., was under investigation.

Marise Green, 49, who lives across the street, said she was reading a book right before the fire.

“And suddenly I heard an explosion and I looked outside and saw the building across the street in flames. In maybe, like, five minutes the fire department came right away, because they’re close by here,” she said. “There was a lot of smoke, a lot of flames. They could not contain the fire and then by 4 o’clock they decided to evacuate because they thought the building could collapse.”

She roused her sleeping daughter, Isabella, 14, grabbed her dogs — Cherry and Pepper — and ran downstairs.

Leonard said firefighters could not prevent a possible collapse.

“We establish our collapse zones. We keep people outside the collapse zones and we will make sure that we have tower ladders here pouring water into the building at a safe distance,” he said.

The sprinkler system had been removed during the renovation, contributing to the swift conflagration, he added.

“There were numerous holes in the floors. They were putting the center shaft, new elevators … all the fire protection features of a normal building have been removed because of the construction,” he said.

The city was reviewing applications filed in August to install a sprinkler and standpipe system, according to the city Buildings Department.

Delshah Capital, which bought the former commercial property for $26.4 million last year, was converting it into a 40,000-square-foot complex called The Dorian, according to company CEO Michael Shah.

The building was slated to rise to 10 stories with 14 units. Penthouses were planned for the seventh through 10th floors, along with retail space on the ground floor.

Delshah expected the project to be completed by the end of 2016 — with lower-floor units going for about $3 million and a penthouse fetching as much as $10 million.

Kay Johnson, 31, who lives at 212 W. 18th St. behind the affected building, said her concierge called residents as others banged on doors to alert everyone to evacuate.

“It was very smoky. I was scared. It was very scary,” Johnson told The Post. “I rushed out with no jacket and wearing slippers… a neighbor loaned me a coat. I came out and I thought something terrible had happened. I’ve never seen so many firemen in one place before.

“It was terrifying….There were scantily clad people everywhere, wearing robes, pajamas and no shoes and there were lots of crying children.”

Lawrence Smith, 62, an artist, who lives at 218 W. 17th St. with his wife, Andrea Torrens, 57, fled after being told to evacuate.

“I woke up to the smell of smoke. I stepped outside and the building was fully engulfed. Flames were shooting out the windows and there was thick smoke everywhere,” Smith said. “We had to evacuate because of the fear the building may collapse. We lost our apartment four years ago in SoHo, on Thompson Street — so this is deja vu all over again.”

His wife was holding a case with their dog, Barns, a 5-year-old Schnauzer mix.

Ann Forster, 57, a publicist who lives on the first floor at 224 W. 17th St., said she woke up to banging on door and windows.

“At first I thought it was just people making noise. I opened the door and saw my neighbors in pajamas and they said we had to evacuate. There was smoke everywhere,” Forster said.

“All you could see through the smoke were flames. It was completely engulfed,” she said about 221 W. 17th St. “It’s terrible. I’m not fully dressed and I have to be at work by 9.”

Ben Feuerherd contributed reporting.