A New York skyscraper is feared to be on the brink of collapse after "continued shifting" was detected.
The 37-storey building, located in Midtown Manhattan is the former home of Pfizer and was under construction to be converted to a residential building.
Hundreds of police cars and ambulances responded to the in New York's streets, with a "frozen zone" established to halt all pedestrian and vehicle travel.
Nine nearby buildings have now been evacuated, including at least two hotels filled with tourists.
New York's socialist Mayor Zohran Mamdani held a press conference at 8am on Tuesday morning, describing the emergency response as an "extremely serious situation".
"The concern is that since we have been on site since the early morning, we have seen continued shift of the structure," he told reporters.
John Esposito, chief of the Fire Department of New York (FDNY) told reporters the high-rise was "moving", warning of the building's "continued shifting".
Renovation work has added an additional four floors to the tallest section of the building, which is to be converted to 1,600 apartments.
Images of the buckled steel beams which have caused an 'extremely serious' situation in New York
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The former Pfizer headquarters were set to be converted to 1,600 apartments
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Architects have described the project as the largest of its kind in New York City history. It was scheduled to be completed in 2027.
Images of the structural columns on the 17th and 21st floors - taken by the FDNY - showed the steel beams nearly bent in half, but at 4.30pm EDT (9.30pm BST), city officials told The New York Times they had not buckled any further.
"It's a very serious situation because the box beams - the steel beams - have started to bend and deflect from the weight," Mr Esposito said.
One construction worker, who had been working on the high-rise at the time, said he had "never seen this before".
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Zohran Mamdani described the building's status as 'extremely serious'
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Images from the FDNY show the building's tilt
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He said: "It's not supposed to happen. Columns are not supposed to bend like that, you know. But who knows? You know, I don't know, honestly, what can happen?"
He added: "I was outside with my guys across the street. Everybody left the building. You know, everybody was evacuated, and that's it."
Nathan Berman, the managing principal and founder of MetroLoft, which is the developer for the apartment conversion, admitted the collapse is likely to delay the conversion work for a few weeks.
He said the two columns had possibly not been sufficiently reinforced, but added that the remaining columns had "picked up the weight".
New York's 'frozen zone' was announced on Tuesday morning, both pedestrian and vehicle transit
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New Yorkers in nine buildings, including two hotels, were evacuated as part of the emergency response
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Just before 7.30pm EDT (12.26 BST), residents of one building near the scene had been told it was safe to return, with other buildings still being assessed, according to one city official.
One of the developers for the project, MetroLoft said in a statement that no injuries has been reported.
A spokesman for MetroLoft said: "The safety of everyone at and surrounding the building is our number one priority.
"We're thankful there were no injuries, and as the Department of Buildings clarified, no debris fell from the building.
"We want to confirm that the affected area is a small section of one of the two buildings on this site.
"As the FDNY. spokesperson noted, the entire building itself is not at risk of collapse."