A construction worker found human skeletal remains inside the basement of a long-vacant, crumbling Queens building – months after a city-issued violation noted the entryway needed to be sealed, cops said.

The NYPD was notified of the chilling discovery just before 2 p.m. Monday, inside the condemned building on Jamaica Avenue near 120th Street in Richmond Hill, authorities said. 

Police could not confirm whether a full body was recovered, or a portion. It was unclear how the person had died.

The building – which neighbors say has been vacant for more than two decades – was slapped with a Department of Buildings violation Nov. 14 for failure to seal up the basement doors’ opening to secure against unauthorized access and safeguard the public.

An earlier complaint raised concerns about the basement“caving in,” with rodents escaping – and calls for action “before someone gets hurt.”

Another complaint notes that the “entire top” of the deteriorating structure is “caved all the way in and is visible from the train that rides past.”

The crumbling structure has a now-shuttered commercial space on the ground floor, with two residential floors above.

One man told The Post he heard the commotion Monday afternoon, but by the time he went outside to see what was going on, the bones had already been taken away.

“They did it quietly,” the 35-year-resident said of the removal, adding that the unsettling find “got to me.”

 “Things happen here but you just don’t hear about it,” he said.

The neighbor said that the building owner told him the space has been unoccupied for 25 years.

“The building had a fast food joint [on the ground floor] – a chicken place there, then they had a deli,” the man said.

“They had tenants on top,” he added. “The building caught fire and they never fixed it, so it was empty all these years.”

“They used to do a lot of drugs in this area. It could be a squatter — who knows.”

Tuesday morning, the ground floor of the building was boarded up, chained and padlocked, with two Department of Buildings work permits in clear view.

“The building’s facade is cracked up the side to the top, [with] visible space between the bricks,” the complaint states. “This building is attached to a residential building with tenants residing there. The building is obviously crumbling from the inside out and needs to be inspected asap.”

A nearby deli worker who would only give his first name, Noel, said his business has been open for 11 years – and during that time, he never saw any residents at the shuttered building.

“[The construction workers] started working there about a week ago,” said Noel, 40. “They should be here already but I don’t see anybody today.”

He said he never caught a glimpse of the remains. 

“I saw the police but I didn’t go to look,” Noel said. “I didn’t know what it was but I knew it was something big because there were a lot of police. After that I heard there were bones there.”