Several Midtown Manhattan blocks were evacuated Tuesday morning after construction workers discovered the structure of a massive office building being converted into residential housing was compromised on the 21^st floor, officials said.

As of 12:45 p.m., the building at 235 E. 42nd Street, has continued to move as engineers and first responders work to secure the site, officials said at a press conference.

New York City Fire Department and Department of Buildings crews raced to the building, which is one block west of the United Nations headquarters, around 8:00 a.m. after workers "observed structural support beams beginning to buckle," the NYPD said.

That caused the 21st through 26th floors of the building to start caving under the stress, officials said.

ABC News obtained video from inside the compromised building that damage.

The 37-story commercial building, formerly the Pfizer headquarters, is currently undergoing renovations to convert it into a residential building, according to the DOB. It is one of the largest office-to-apartment conversion projects in city history, officials said.

There were no reported injuries and all construction workers were safely evacuated, according to police.

"The building has continued to move since we have been on scene," Fire Chief John Esposito told reporters at a news conference. "It does mean it is not yet stable."

Structural engineers are monitoring the building's movement from the outside, New York City Buildings Commissioner Ahmed Tigani told reporters.

"There is extensive work going on now to evaluate the situation," he said.

Once it's deemed safe to enter, workers will begin shoring up the building with emergency trusses, according to Tigani.

The fear, officials said, is a partial collapse, which could be internal.  A full collapse onto the street is less likely, Esposito said. 

Metro Loft, the developer of the conversion project, said in a statement that it is working with the Department of Buildings as it investigates the situation.

"The safety of our workers and the public has always been, and remains, our top priority," the developer said.

This building has seven violations between July and December 2025, resulting in more than $32,000 in fines issued, according to DOB records.

New York City Mayor Zohran Mamdani said that a frozen zone was set up between 40th and 45th Streets and 1st and 3rd Avenues. Those streets are closed to both pedestrian and vehicular traffic.

The mayor said that seven other buildings near 235 East 42nd Street were also evacuated, including a nearby Hampton Inn, according to officials.

Mamdani said at an unrelated news conference earlier Tuesday morning that among the evacuated locations was a school with 400 students.

"I want to be honest with New Yorkers that this is a fast-developing situation. We are taking it minute by minute," he told reporters.

The mayor added that the people living and working in the frozen zone will get updates and thanked them for cooperating with the evacuations.

Gov. Kathy Hochul released a statement, saying she is in contact with city officials and state building inspectors are also on the scene.

ABC News' Nicole Katchis and Tonya Simpson contributed to this report.