They were identified as Melissa Barthelemy, 27, from the Bronx; Amber Lynn Costello, 27, from North Babylon; and Maureen Brainard-Barnes, 25, from Norwich, Conn.
All three women had advertised themselves online as escorts prior to their deaths, and investigators said Monday that they are again returning to the serial killer theory.
"Their deaths are a direct result of their business as prostitutes," Suffolk County District Attorney Thomas Spota reportedly said. "I sincerely hope that people who are engaged in a similar business as these four young women would come forward. They certainly must have some information."
Spota also added that while all four women shared the same profession, police have now also determined that the actual cause of death appears to be the same.
Police are now sifting through email correspondence and trying to determine who had the last online contact with the women.
The women's bodies were originally found dumped within 500 feet of each other in a brush-filled area, and while Suffolk County police initially suspected it was a case of a serial killer, they backed away from the theory over the following weeks.
Medical examiners identified the first of the four bodies last week, 22-year-old Megan Waterman.
The victim had been missing since June 6, 2010 and was last seen at a Hauppauge Holiday Inn Express near exit 56 of the Long Island Expressway.
Waterman, of Scarborough, Maine, had been working as an escort on Craigslist, but was reportedly with her boyfriend that night at the hotel.
Authorities were looking for a New Jersey woman, also a Craigslist escort, when they came across the four bodies on Long Island. Police noted that the Long Island case bears striking similarities to a rash of Craigslist escort killins in Atlantic City, NJ.