Two structural support beams on the 21st floor of a 37-story under-construction building in Manhattan started buckling Tuesday morning, triggering a mass evacuation, street closures and a large emergency response, officials say.

The FDNY said it got a call around 8 a.m. about bricks falling from the building at 235 East 42nd Street, between Second and Third avenues. The NYPD says it got a 911 call about the incident less than 15 minutes later.

When cops got to the scene, the NYPD says officers were told that construction workers on the 21st floor of the commercial building saw the columns beginning to collapse.

Raw footage from inside, taken by a construction worker, showed crumbling steel beams on the 21st floor.