A section of a 20-storey residential building partially collapsed in New York City on Wednesday morning, and authorities say there are no injuries.

Firefighters and emergency responders searched into the afternoon for anyone who may have been trapped under the mounds of rubble outside the building, which is part of a public housing development in the Bronx.

The whole building just - you heard a loud boom, and the thing just exploded, and it fell down just like that, said one witness who spoke with CBS News, BBC's US partner.

Another witness mentioned, Somebody in the building next to me, they said that their window even fell, and it's on the 16th floor.

The collapse seems to have originated from an explosion in the ventilation shaft of a boiler room, according to fire commissioner Robert Tucker. There were no reports of apartment damage, but some residents were evacuated while others returned with gas shut off as authorities investigate.

Mayor Eric Adams noted that investigations would focus on whether a gas leak triggered the explosion. The NYC Housing Authority, which manages the complex, stated that it is looking into the incident and assessing the extent of the damage.

In public records, the NYC Department of Buildings had issued a partial stop work order related to plumbing violations in June. Additionally, there are three open violations against the property concerning non-safety issues on boilers.

A recent fire in the same building left a teenage girl in critical condition, but reports indicate she is recovering now.

We were lucky that this emergency didn't result in a loss of life, that it didn't turn into a tragedy, said Amanda Septimo, an assembly member who represents the district. But we can't be relying on luck to keep our community safe.