A city worker and his two buddies were busted after they climbed down a Brooklyn manhole to hunt for “treasures” in the sewers, police sources said Thursday.

Marquis Evans, 21, who works part-time for the Department of Environmental Protection, and pals Damien Nieves, 35, and David Hannibal, 45, all of Brooklyn, were spotted by a passer-by prying off a manhole cover on East 35th Street near Avenue H in Flatbush and climbing into the hole around 7:30 p.m. Wednesday, cops said.

Evans, the ringleader of the sewer excursion, popped the manhole for his buddies and covered it back up, according to police. He was supposed let them back out at 12:30 a.m., after their buried-treasure expedition, sources said.

“He let them in to go down and do their scavenger hunt,” a law-enforcement source said, adding that Evans never actually scoured the sewers with his buddies but just gave them access.

NYPD Commissioner Bill Bratton said Thursday that he wouldn’t be caught anywhere near the grimy city sewers.

“God knows what they were looking for,” Bratton said. “I know damn sure I wouldn’t be crawling through the sewers of New York, but these three evidently were up to something down there.”

Cops arrived at the scene at around 9:30 p.m., and Evans, who was still there, was taken into custody, police said.

“We asked [Evans] what he did – he said he led two people down there to search for merchandise that may have been discarded,” NYPD Chief of Detectives Robert Boyce said Thursday.

Cops and firefighters then combed through the sewer tunnels for four hours before finding the other two men, police said.

Authorities did not go down the manhole at first because of “dangerous gases,” sources said.

One of the men later told investigators that they were down their looking for jewelry and other valuables, sources said.

Authorities believe Evans led his friends down the sewers several times in the past to go on the “scavenger hunts,” sources said.

“There are probably about 5,000 manholes in New York City. We’re not going to weld them all shut,” said Boyce. “Anyone who wants to go below the streets, unfortunately, can do it by prying.”

Boyce said there are counterterrorism issues involved, “but we don’t think that’s what it is.”

The three men were hit with criminal-trespassing charges. Evans was also busted on charges of reckless endangerment, criminal facilitation, possession of marijuana and disorderly conduct.

The DEP said Evans has been suspended.

“Entering a sewer without proper authorization and training is illegal, incredibly irresponsible, and dangerous,” agency spokesman Christopher Gilbride said in a statement. “Illegally accessing any confined space with potentially hazardous materials or conditions risks the safety of the trespassers as well as the first responders who are called on to rescue them. The employee in question will be suspended pending further investigation.”

All three men were awaiting arraignment in Brooklyn Criminal Court on Thursday afternoon.