An explosion destroyed two blocks of flats in New York City yesterday, killing at least two people and injuring 17 others.
The fire department said more than a dozen people were missing.
It also said two of those injured have life-threatening injuries.
A utility company said a resident in a nearby building in East Harlem reported smelling gas shortly before the explosion, although the cause of the blast has yet to be determined.
The odour was believed to have been coming from outside.
The company sent two crews to investigate the report, but they arrived just after the explosion.
The blast centred on a five-storey building near Park Avenue and 116th Street, and it sent huge flames and billowing smoke into the air.
Pavements in a large surrounding area were littered with broken glass from windows. Witnesses said the blast was so powerful it knocked food off the shelves of nearby shops.
Police, some wearing gas masks, handed out medical masks to residents and onlookers because of the thick smoke shrouding the area.
Eoin Hayes, 26, said the explosion shook his block of flats in Harlem at about 9.30am local time. He ran to the window and saw flames consuming one building and smoke rising into the air.
“I was in my bedroom and the explosion went off, it kind of shook the whole building,” he said. “You could feel the vibrations going through the building.”
The explosion occurred close to elevated train tracks. Services were suspended while debris was removed.
The fire department said it sent nearly 170 members to the scene.
New York City mayor Bill de Blasio visited the scene, later confirming that a “number” of people were missing.
The two confirmed dead were both women.
Meanwhile, a spokes- man for utility firm Con Edison said it is working with the fire department “checking gas lines”. He added: “We’re working to isolate any leaks and make the area safe.”
Waldemar Infante, 24, a porter from a nearby residential building who was working in the basement when the explosion occurred, said: “It felt like an earthquake had rattled my whole building.
“There were glass shards everywhere on the ground and all the stores had their windows blown out.”
The mayor added that some of those unaccounted for may have fled to safety, but said the city would make every effort to locate everyone.
A hotline was being set up for concerned relatives, he added.
Con Edison was shutting down all gas mains going into the buildings.
One of the destroyed residential buildings housed a piano shop on the ground floor, the other a church.
Building department records show the building with the church received permits to instal new gas piping in June.
Eusebio Perez, 48, a piano technician who lived in one of the buildings but was at work at the time of the blast, said: “There’s nothing left. Just a bunch of bricks and wood. I only have what I’m wearing.”