Media playback is unsupported on your device Media caption New York City Mayor Bill de Blasio: "This is a tragedy of the worst kind"

At least six people have died and several are missing after a gas leak sparked an explosion which levelled two buildings in New York City.

Scores of others were injured in the incident, which sent smoke billowing into the city sky.

Rescue crews began searching the debris on Wednesday evening for victims after the fire was finally put out.

Train services to and from Grand Central Terminal have been restored after a complete halt earlier.

Image copyright AP Image caption The force of the explosion destroyed two buildings and smashed nearby windows

Image copyright AP Image caption Nearly 200 firefighters were dispatched to try to extinguish the fire that followed the blast

Missing people

As the search-and-rescue operation continued under floodlights on Wednesday night, the emergency services confirmed that the death toll had risen first to four, then to five and to six, with several people still missing.

Earlier, New York City Mayor Bill de Blasio said in a news conference from the scene that the gas leak had been reported to the utility company 15 minutes before the blast on Wednesday morning.

Media playback is unsupported on your device Media caption "We heard 'boom' and all the windows broke down"

Mr de Blasio said the "major explosion" had destroyed two buildings and heavily damaged other structures.

As night fell, rescue crews were finally able to search for victims in the debris after the fire raged for most of the day.

At the scene A dense plume of smoke in the skies of Manhattan is a sight for New Yorkers that stirs bad memories and spreads fear - especially early in the morning. But despite the early presence of the FBI as a precautionary measure it soon became clear this was a gas explosion rather than foul play. The intensity of the blaze, which took hours to extinguish, made it all the more difficult for emergency crews. They could not carry out a search of the rubble. The choking smoke added to the immediate chaos at the scene, as local people rushed to find loved ones. More than a dozen people were reported missing. The hope is that they are alive and simply can't be contacted. The fear is that some were unable to escape.

Heavy equipment, including a bulldozer, helped clear the remnants of two multi-storey buildings. Thermal imaging cameras were brought in to identify bodies or pockets of fire inside the mountain of debris.

The New York fire department said 22 people had been hurt, but a tally of local hospitals by ABC News found that 64 had been admitted with injuries as a result of the incident.

That figure included seven children, one of whom was in a critical condition.

The utility company, Con Edison, says a resident in a nearby building reported smelling gas shortly before the explosion.

Streets and pavements around the site were littered with broken glass from shattered windows.

The blast scattered debris across nearby rooftops, correspondents say, destroying adjoining five-storey buildings in a largely Latino working-class neighbourhood.

Witnesses reported the powerful blast knocked items off shelves in nearby shops.

Authorities in the area were said to be handing out medical masks to residents due to the thick white smoke at the scene.

Image copyright Reuters Image caption Firefighters begin searching through the rubble of the two buildings

A witness told the BBC "there was just a lot of panic" following the explosion.

Dan Scarvino had just emerged on to a nearby train platform when "suddenly a plume of smoke came out of nowhere".

"I've never seen anything like it," he added.

A witness told the New York Daily News she had smelled gas "for weeks" before the explosion.

"We saw people flying out of the window... those are my neighbours," Ashley Rivera said.

Another witness told the newspaper he heard two loud explosions that shook the barber shop where he works.

"It was loud, like boom, boom!" Mitch Abreu said. "It rocked the whole block."

"It looked like the [Twin] Towers all over again. People covered in dust and covering their mouths."

Image copyright Google/Reuters Image caption Before and after at the collapsed buildings

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