Instead of plowing, they got plowed.

A group of on-duty Sanitation supervisors is under investigation for allegedly buying booze and chilling in their cozy department car for hours Monday night after the blizzard stranded a bus and three snowplows blocks away.

The city Department of Investigation is probing the incident after witnesses said four snow blowers blew off their duties to get blitzed, buying two six-packs of beer from a Brooklyn bodega. The workers then walked five blocks to their car, which was in 20 inches of snow in the middle of 18th at McDonald avenues near the F train entrance, passing the stuck bus and idle plows on 18th Avenue between Third and Fourth streets.

The four remained in the idling sedan until morning — then told their bosses they could do nothing about the blizzard because they had run out of gas, one witness said.

“They just sat in their car all night with the heat running,” the witness said.

MORE WORKERS CATCH A ‘COLD’

DAVID SEIFMAN: SCHEDULES REVEAL TALE OF TWO MAYORS

MICHAEL GOODWIN: EMPEROR MIKE’S SNOW BLINDNESS

Customers who saw the group buying beer at the Ocean Mini Mart at 3917 18th Ave. in Kensington shouted at the workers.

“They were saying, ‘How can you do this? You should be outside!’ ” a witness told The Post.

But the Sanitation team was unmoved.

“One guy said, ‘Don’t worry about it. We know what we’re doing,’ ” the witness recalled.

A block from the deli, six riders remained on the snow-stalled bus all night.

The supervisors had shown up at the deli near Ocean Parkway at 8 p.m. when a smiling, uniformed Sanitation honcho bought a six-pack of Heineken Light, the witnesses said. About 30 minutes later, another worker from the group bought a six-pack of Corona Light.

Later, they ducked inside their car and hunkered down.

“I saw them drinking, but I’m not sure what it was,” said a witness who lives in the area.

In the morning, the four men returned to the deli, where they were heard telling their bosses over the phone that their car had run out of gas.

“This guy was on his cell and said, ‘We’re out of fuel,’ ” a witness said.

Department of Investigation Assistant Commissioner Keith Schwam said “we’re looking into what happened.”

The DOI is also investigating whether Sanitation workers contributed to the chaos with an organized slowdown.

Yesterday, city officials claimed every street in the city had seen a plow and said garbage pickups would resume tomorrow, starting with street-corner cans and, possibly, residential trash.

Additional reporting by C.J. Sullivan

brad.hamilton@nypost.com

