New York City building regulators said the conversion of a Midtown Manhattan office tower into residences must be paused while officials investigate what caused columns inside the building to fail, leading to a massive emergency response that briefly shut down one of the busiest corridors of the city.

The Department of Buildings issued a partial stop-work order to halt all non-emergency construction at the site, where steel columns buckled on the 21st floor, causing structural damage on multiple others levels of the building.