At least one building collapsed and several more were thought to be on fire following a massive explosive in Harlem that left nearly a dozen people injured, early reports suggest.

As emergency crews and firemen from across New York City rushed to 116th Street and Park Avenue on the Upper East Side, a large plume of dark smoke fanned across the city just as the morning rush hour was coming to an end.

It was visible within minutes from the bustling heart of commercial Midtown.

Witnesses, many on their way to work and some still in their apartments, said they had heard a very loud blast from where the apartment building once stood at East 115th St and Park Avenue in Harlem.

First reports said the building, which is thought to have been about five storeys, had been devastated by the blast.

A car that had been parked outside had also been incinerated presumably in the fierce fire that followed.

"It shook my building and I am six blocks south," one nearby resident told MSNBC News.

"It did feel like a big clap of thunder. It is a little worrying to know the cause." He said that even though he lives six blocks away from the fire his building was shaken by the explosion.

No fewer than 39 units of the New York Fire Department were racing to the zone, officials said, involving almost 200 firemen.

First glimpses of the site revealed that debris had been spread over a large area, including across the tracks of a main commuter train line into New York from the North and Connecticut. One of the busiest train corridors in the nation, it has been shut down pending the scene being brought under control.

While the neighbourhood is among the most densely populated in New York there was still no early word on numbers of possible victims or indeed whether any residents of the structure or local workers might have been trapped by the collapse.

The leading theory of the cause of the blast was that it might have been some kind of gas explosion.
© Andrew Burton/Getty ImagesHeavy smoke pours from the debris as FDNY responds to a 5-alarm fire and building collapse at 1646 Park Ave in the Harlem neighborhood of Manhattan in New York

Investigators will be trying to determine if any work was being done in the vicinity, perhaps on gas lines, in the minutes before it happened. Most of the buildings in this area feature commercial spaces and shops on the street level and then apartments above them.

While the address was on Park Avenue, the neighbourhood involved is far less ritzy than some zip codes just a few blocks to its south where the transition begins from some of Manhattan's most exclusive districts on the Upper East Side, particularly along Park Avenue, to the less salubrious climes of Harlem happens.

While an accident seemed the likely cause, for many New Yorkers the sight of such a large plume rising above Manhattan, particularly at this hour of the morning, is bound to evoke painful memories of 9/11 even though on that day the smoke was coming from the far south of the island.

Another resident of the area spoke of "debris in the air" that he saw rising after hearing the boom. "It looked like like paper and other products", he said.
© AP Photo/Jeremy SailingThe explosion leveled two apartment buildings, and sent flames and billowing black smoke above the skyline