New York City police are trying to trace eight people who are unaccounted for after an apparent gas explosion in Manhattan.

Officers are trying to determine whether six people reported missing are connected to the blast in the fashionable East Village. They are not believed to have been inside the three buildings levelled by the explosion.

Police said earlier that another two people were so far unaccounted for but had not yet officially been classified as missing persons.

Restaurant worker Moises Lucon and diner Nicholas Figueroa were in one of the buildings that were destroyed.

Police Commissioner William Bratton said the search is "very complex".

At least 19 people were injured, four critically. Preliminary evidence suggests a gas explosion was sparked by plumbing and gas work inside a building.

Inspectors discovered faulty work an hour before the blast, which caused the building to collapse.

Craig Ivey, president of utility company Con Edison, said a plumber was doing work connected to a gas service upgrade and inspectors had been there to check on a planned meter installation about an hour before the fire.

But the work failed the inspection, partly because a space for the new meters was not big enough and the inspectors said gas could not be introduced to that part of the building.

The fire spread to nearby buildings, scattering debris across surrounding streets in the heart of the East Village.

Orange flames billowed and smoke could be seen and smelled for miles after the blaze, in an area of old tenement buildings that are home to students and long-time residents near New York University and Washington Square Park.

About 250 firefighters battled the blazes and the area was evacuated as the city's health department advised residents to keep their windows closed because of the smoke.

Tyler Figueroa said his 23-year-old brother Nicholas disappeared after going on a date at a sushi restaurant that was levelled by the explosion.

Mr Figueroa, 19, said the couple were paying for their meal when the blast occurred, and that his brother's date, who is in hospital, remembers only stumbling outside before losing consciousness.

"I just pray my brother shows up," he said.

Firefighters worked through the night to put out fires, pouring large volumes of water over the rubble, a fire department spokesman said. Light rain this morning tamped down much of the acrid burning smell, but neighbours said they could barely sleep for the sirens and stench of the burning buildings through the night.

The explosion scuppered performances of hit stage show Stomp, which was being staged at The Orpheum Theatre at 126 Second Avenue, a few doors from the blast site.

Producers said five shows scheduled for today, tomorrow and Sunday had been scrapped.

Ticket-holders were advised to return or exchange tickets at the point of purchase.