New York City authorities on Tuesday warned that a 37-story building under construction in the heart of the city could at least partially collapse, after first responders answered reports of falling bricks at the site.

The New York City Fire Department evacuated the high-rise building at 235 East 42nd Street and surrounding buildings Tuesday morning due to fears about floors 21 through 26 of the high-rise building caving in while it is being redeveloped into residential property, according to the FDNY. Officials said they are conducting “a major technical rescue response” at the building. In an update on the situation hours later, Mayor Zohran Mamdani said the building “remains unstable,” but explained assessments of the building are changing by the minute as the structure continues to shift.