The ambitious office-to-residential conversion added new construction to an existing building, causing supporting columns to buckle and steel beams to bend.

New York City has bet heavily on converting aging office buildings into apartments to help ease a housing shortage. But the threat of a partial collapse Tuesday by one such conversion in progress highlighted the significant challenges of those construction projects.

A Midtown Manhattan high-rise building was evacuated Tuesday morning after authorities said it was at risk of collapsing. The 38-story building at 235 East 42nd Street was once the corporate headquarters for the pharmaceutical company Pfizer.

The Midtown building under construction had bricks tumble into the street during Tuesday's morning rush hour, forcing buildings to evacuate, officials said.

Crews are making progress in their effort to stabilize an under-construction Midtown Manhattan building that was evacuated Tuesday after structural columns buckled. Follow for live updates.