New York City investigators and prosecutors in Manhattan have begun a preliminary criminal investigation into a Midtown building where structural issues occurred earlier this week. A city official and a source with knowledge of the situation provided this information.

The New York City Department of Investigation and the Manhattan district attorney’s office initiated the inquiry, which was still in its early stages as of Friday. The specific focus of the investigation and the individuals or entities involved were not yet determined, partly due to ongoing efforts to stabilize the 37-story high-rise.

The building, located at 235 East 42nd Street, was under conversion from office space to residential apartments. On Tuesday, workers noticed cracks in the concrete floors and buckling columns on the 21st floor, which triggered evacuations and an emergency response.

This criminal inquiry is expected to be both complex and labor-intensive. The construction project at the site, formerly the headquarters of the drugmaker Pfizer, was planned to be the largest residential conversion in the United States. Such projects often involve numerous companies, subcontractors, and developers, each with distinct roles and responsibilities.

Determining what transpired and the reasons behind it, alongside assessing any potential criminal liability, may require months or even years. There is also a possibility that the inquiry might conclude without any charges being filed.