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

Two structural support beams on an under-construction building in Manhattan started buckling Tuesday morning, triggering a large emergency response, officials say.

A luxury Brooklyn high-rise was pelted with illegal fireworks July 4 — damaging its windows, showering onlookers with sparks and sending rooftop party-goers fleeing, fuming tenants told The Post. No one was seriously hurt as the rogue pyrotechnics were launched at the tony apartment tower from the street,

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.

Plans have been to add a dozen more stories atop the 38-story office building that's being converted into apartments.

Structural problems at a building in Midtown Manhattan continue to snarl traffic as repairs and inspections proceed. The area was evacuated this week when the building was deemed at risk of collapse.