A high-rise Midtown Manhattan office building being converted to apartments showed signs of collapsing on Tuesday, prompting evacuations, street closings and an emergency response that disrupted the morning rush around Grand Central Terminal.

But on Tuesday night, New York City’s buildings commissioner, Ahmed Tigani, sought to reassure the public, even as he said that the neighborhood around the building may remain in a tense situation “for the next couple of days.”

“I can say right now the building is stable,” Mr. Tigani said. “We feel confident in the emergency plan we have now.”

The Fire Department received a call about falling bricks near the building, 235 East 42nd Street, just before 8 a.m., officials said. The building, the former corporate headquarters of the pharmaceutical giant Pfizer, is being transformed into a 1,600-unit residential property that one of its developers has said is the largest such conversion in the United States.

A safety manager at the building, which has 37 stories, reported on Tuesday that a steel beam on the 21st floor was compromised, city Buildings Department records show. Two support columns inside the building were buckling, and several upper floors were sagging, fire officials said.

Here’s what else to know:

Was anyone hurt amid the threat of a collapse?

There were no injuries, fire officials said. Construction workers were evacuated from the building, and workers were also cleared from adjoining properties at 225 and 221 East 43rd Street as a precaution, fire officials said.

Cliff Johnsen, the business agent for Steamfitters Local 638, said his union’s members were evacuated from 235 East 42nd Street after beams started to bend. “The north side of that building is crumbling,” he said. “I-beams are bending like cigarettes in there.”

A “frozen zone” had been established from 40th Street to 45th Street and from First Avenue to Third Avenue as a further precaution, Mayor Zohran Mamdani said at a news conference.

What kind of work is being done at the building?

The former Pfizer headquarters — two buildings, 235 and 219 East 42nd Street, which were combined — is being turned into an apartment complex as part of a broader effort to use empty Manhattan office buildings to help ease the city’s housing crunch.

The project, a joint effort by Metro Loft and David Werner Real Estate, began in 2024 and had been expected to be finished next year. In addition to redesigning 235 East 42nd Street, the developers’ plans call for adding 11 stories to the existing 22 at 219 East 42nd Street, Mr. Tigani said.

Four hundred of the planned 1,602 apartments were earmarked as affordable. The design also includes more than 100,000 square feet of amenities such as shops, a rooftop pool and a fitness center.

Metro Loft said in a statement that it was aware of problems with the building and was working with the Buildings Department to “understand the full scope of the situation.”

Reporting was contributed by Liam Stack, Claire Fahy, Mihir Zaveri, Caitlyn Freeman, Chelsia Rose Marcius, Matthew Haag, Hurubie Meko and Davaughnia Wilson.