After the deadly collapse of a parking structure in lower Manhattan, New York City building officials swept through dozens of parking garages and ordered four of them to immediately shutter because of structural defects that “deteriorated to the point where they were now posing an immediate threat to public safety.”

Two of the parking garages have apartments above them — a 25-story high-rise in downtown Manhattan and an eight-story building in Chinatown — but officials said the residential areas appear to be in no danger.

City officials directed the owners of the parking facilities to make immediate repairs to corroded concrete and other damage.

Inspections were launched soon after a three-story stand-alone parking structure, about a century old, imploded into shards of concrete and twisted metal on April 18, crushing to death its manager.

“This work was done in the interest of public safety, and out of an abundance of caution,” said Department of Buildings spokesperson Andrew Rudansky.

“During our sweep of 78 parking structures, we found four locations where structural concerns necessitated areas of the buildings to be immediately vacated,” he said.

The city last year began mandating that parking structures be inspected by owners at least once every six years. The first wave of garages, located from the southern tip of Manhattan to the lower Central Park area, have until the end of the year to complete initial inspections.

The structure that collapsed earlier this month had not yet completed its required inspection, city officials said.

Why it collapsed is still under investigation but the building had been previously cited for various structural defects, including signs of corrosion in concrete called “spalling.”

Two decades ago, city inspectors cited the property owner for failing to properly maintain the building, finding at the time that there were “cracks and defects” in the concrete. A more recent inspection in fall 2013 showed no further structural issues, building officials said.

The garage, a few blocks from City Hall and the Brooklyn Bridge, caved in just as the first trickles of patrons were beginning to return to the garage after work.

The collapse shook nearby buildings and terrified people who described the sound of the falling structure as a massive explosion and compared the experience to a violent earthquake.

Enterprise Ann Parking, which operated the garage on Ann Street, said it was cooperating with authorities on the probe.

Inspectors have since visited 17 parking garages managed by the same company, as well as 61 additional buildings with parking garages that had open structural citations.

They found four properties with structural damage in the parking garages where the damage was so bad, the city issued vacate orders to at least parts of the structures.

Underneath the 25-story building in lower Manhattan, inspectors found concrete slabs “extensively corroded, with spalled concrete on the underside of two-floor slab ceilings.” As a result, more than half of the garage is now off-limits and its operators ordered to provide protected pathways in those places.

But engineers found no need to vacate any residential areas of the building.

Similarly, building officials said residents could stay put in a Chinatown apartment building despite finding “numerous severely deteriorated and rusted steel beams, with excessive cracked and spalling concrete piers.”

A two-story parking structure in Brooklyn was in such disrepair, the city said, that it ordered the shuttering of the entire structure. Another two-story structure in the borough was partially closed because of extensively corroded beams and deteriorated vehicle ramps.

The four buildings can’t reopen until repairs are made and pass inspection.

Because inspections of parking garages continue, officials said there could be more enforcement action to come.

Meanwhile, crews continue clearing debris from the fallen structure.

Manhattan District Attorney Alvin Bragg had opened an investigation into the collapse.

An initial investigation by the building department noted that all three floors of the garage partially or completely collapsed. The garage’s rear wall partially collapsed, and the front facade bulged.

(AP)