At least four people have died after a building in New York City collapsed into an open construction site on Wednesday afternoon.

Nineteen others have been injured, of whom four are in a critical condition, according to the BBC's US partner CBS News, which cited local officials.

The collapse sparked a massive search-and-rescue operation, with more than 250 first responders going to the scene of the fallen three-storey building in Brooklyn.

Aerial footage has shown firefighters pulling a survivor, covered in dust, out of the debris on a stretcher. She was later said to have been a pregnant woman.

Officials previously said they did not know how many others are missing. The BBC has contacted the New York City Fire Department (FDNY) for further comment.

An investigation is under way into what caused the sudden collapse.

Witnesses described a terrifying sound as the building came down at about 16:00 local time (21:00 GMT).

"I live literally right behind the building," one woman, Emmanuella Carilus, told the New York Times. "It sounded like a big boom and you just heard a bunch of screaming."

The newspaper published images showing a crowd of fire trucks and police vehicles at the same, and wrote that the noise of sirens had not stopped in the area.

"I've never seen anything like this," said another witness, named only as Dashik, who spoke to local television station PIX 11.

Officials are yet to identify those who died or were injured.

Some pictures of the collapsed building, on Flatbush Avenue in Brooklyn, show an entire side of it gone, with bedrooms and closets exposed. Among the debris, smashed concrete and twisted metal, are household items and clothes.

New York City Mayor Zohran Mamdani joined emergency responders at the scene, praising them for their rapid response.

They "arrived in under a minute and have spent hours working in dangerous and highly technical conditions to rescue New Yorkers," he later wrote on X.

The Brooklyn building was built in 1930, city records show, according to CBS, the BBC's US partner.

At the adjacent construction site, where plans have been approved for a new building, active work was going on when the incident occurred, according to FDNY Chief of Department John Esposito.

The activity was described by another official as "excavation work". It was not immediately clear whether the work had anything to do with the collapse of the neighbouring building.

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