Two NYPD cops are being eyed in the Long Island serial slayings after investigators learned they got into trouble for hiring prostitutes while working for the department, according to sources familiar with the probe.

One cop was forced out of the job in the 1990s when his supervisors learned he spent time pursuing hookers and paying street walkers and down-and-out women for sex while he was supposed to be on patrol.

An internal investigation led to his resigning under pressure, one source said.

The other officer still works for the NYPD but was stripped of his gun and badge years ago because he allegedly assaulted a prostitute and got arrested during a sting operation.


MYSTERY:One retired and one working NYPD cop -- both with past troubles involving prostitutes -- are being eyed in the ongoing investigation of the serial killings of call girls Maureen Brainard-Barnes (above), Megan Waterman, Amber Lynn Costello and Melissa Barthelemy.

The woman complained to police supervisors about the officer but no criminal charges were filed and an internal probe went nowhere, sources said.

The patrolman was allowed to return to the force, they said, though he was placed on modified duty -- transferred to a paper-pushing job in Manhattan where he's not allowed to make arrests or respond to emergencies.

"They couldn't prove anything, but they didn't trust him," said one source.

It's unclear if the disgraced cops know each other or what evidence investigators might have against them in the serial murders.

The Suffolk County Police Department would not comment for this story, and prosecutors did not return messages.

Sources said Suffolk County detectives began looking at the NYPD cops last month after determining the killer likely worked in law enforcement or was familiar with police techniques.

They've focused on how the murderer abducted his victims and if he used insider knowledge to avoid being detected.

Investigators suspect the killer hired the hookers through Craigslist, using a disposable and untraceable cellphone to make appointments.

He also used the cellphone of one victim to call and taunt the woman's teenage sister after he'd abducted her.

Cops traced two of those calls -- to Midtown and Massapequa, LI, which is not far from where the killer ditched the bodies of four hookers just off sand-swept Ocean Parkway near Gilgo Beach.

He'd strangled them, removed all their clothing and wrapped the corpses in burlap sacks before leaving the bodies in thick brush off the desolate causeway.

The four call girls found last year have been identified as Amber Lynn Costello, 27, of North Babylon, LI; Megan Waterman, 22, of Scarborough, Maine; Melissa Barthelemy, 24, who went missing from The Bronx; and Maureen Brainard-Barnes, 25, of Norwich, Conn.

The cops are not the sole focus of the investigation, which has expanded over the last several weeks, sources said.