Most of the professors named in two complaints filed with the college have been longtime fixtures in John Jay’s anthropology and sociology departments who have done extensive research on the history of drug use and prostitution.

The allegations, if proven, would suggest that a small group of faculty at the Midtown campus, long the choice of police and correction officers and others in law enforcement, presided over an academic underworld. Drug use and sex were said to be common in the offices of some professors and in an area known as “the Swamp” in one of the school’s buildings.

One question looming over the investigation, two of the people briefed on it said, is why the college, which has been aware of the allegations since at least May, conducted an internal review before contacting the police or prosecutors. The college has close ties to law enforcement.

Security officers for the college, apparently in mid-August, found significant quantities of drugs and drug paraphernalia during the internal inquiry, but they did not contact the police about the seizures until this month, two of the people said.

And when they did, they turned the drugs over to the police without disclosing their inquiry or the circumstances under which they were recovered, one of the people said.