At least one person was killed and five others were injured Tuesday when a large portion of a parking garage collapsed in southern Manhattan, New York, city officials said.

“There were six workers in the building at the time of its collapse. The four of them were admitted to hospital and are in stable condition. One person is dead and one person refused treatment,” New York City Fire Marshal John Esposito said during a news conference.

Images circulating on social media sites show cars, some of which have been piled on top of each other or overturned, and smoke billowing from the collapsed building.

The structure is “unstable”, said the mayor of New York, Eric Adams, clarifying that the operation to ascertain whether there are others trapped in the debris remains in progress.

The parking lot collapsed “down to the basement,” a city official said.

Authorities are using UAVs and a robotic “dog” to avoid deploying rescue crews inside the building, as the part of it that remains standing is still at risk of collapsing.