New York (CNN) -- Investigators in New York said Sunday they are looking into a report that four sanitation supervisors assigned to clean up after last week's monster blizzard instead bought beer and sat in their car.

"We urge all members of the public, most especially City employees, to call us with any information about this matter or with any provable information about deliberate inaction or wrongdoing relating to the snow storm," said Department of Investigation Commissioner Rose Gill Hearn in a statement.

She said the department "has been working 24/7 on this investigation and we continue to pursue leads about potential deliberate wrongdoing by action or inaction relating to the snowstorm."

Investigators responded to an article published by the New York Post on Sunday, which alleged that a group of on-duty sanitation supervisors bought beer and sat in their department car for hours last Monday night. Citing an unnamed witness, the paper said the four supervisors in Brooklyn later told their bosses they ran out of gas.

The DOI commissioner said a video that reportedly showed store surveillance evidence related to the allegation had been "over ridden."

"We are taking steps to try and reconstruct who was in the store," she said.

The New York City Department of Sanitation has drawn sharp criticism since last week's blizzard that blanketed much of the Northeast.

Rumors have swirled that supervisors ordered rank-and-file workers to slow down cleanup efforts in retaliation for the city's belt-tightening measures.

New York City Councilman Dan Halloran said three sanitation workers and two Department of Transportation supervisors came to his office saying their supervisors ordered the slowdown, telling workers, "the mayor will see how much he needs us" and "there will be plenty of overtime."

Sanitation Commissioner John Doherty said he had not seen evidence of a worker protest. "But we have to look into that," he said.

The head of New York's sanitation workers union, Harry Nespoli, also said he was not aware of any slowdown and doubted there was a protest by workers.

Investigators have so far tracked down and spoken with at least two of the five workers who claimed they were told to slow down or not plow, according to Halloran.

"They (investigators) are leaving no stone unturned. They're going gangbusters on this and sparing no expense," he said.

Halloran also said he has seen city reports indicating that 400 sanitation workers called out sick and another 100 said they had the equivalent of an emergency two days after the storm hit last Sunday.

"That's about 10% of the work force of 5,600. It's unheard of," he said. Normally, Halloran said, 2% to 4% of workers call in sick.

Nespoli said the work force numbers around 5,800, adding that he did not know whether the other numbers Halloran provided are correct.

Calls to the city's Sanitation Department were not immediately returned to clarify the number.

Nespoli does not represent the workers accused of buying beer during work hours. As supervisors, those workers belong to the Sanitation Officers Association Local 444, he said.

Association President Joseph Mannion said there was no coordinated slowdown among supervisors.

On Thursday, the association posted comments denying allegations of a slowdown. "When you look around your neighborhood and wonder what the heck happened with the City's snow fighting ability you don't have to look any further than City Hall," the website said.

Nespoli blamed high winds and mechanical failures for the slower-than-usual response.

"My people have been working 12- to 14-hour shifts, cleaning up the city and trying to get everything nice and clear for tomorrow when schools are back," he said.

CNN's Susan Candiotti and Cheryl Robinson contributed to this report.