A law enforcement official told The Associated Press on Thursday that police have not been contacted by any other potential victims since Philip Markoff's arrest last week.
The official spoke on condition of anonymity because he was not authorized to discuss the case.
Markoff is charged with murder in the April 14 killing of Julissa Brisman, a 25-year-old masseuse from New York City who he allegedly met at a posh Boston hotel through Craigslist. He's also accused of robbing another masseuse he met at a different Boston hotel, also through Craigslist.
Markoff is also being investigated in an attempted robbery of a woman at a Rhode Island hotel.
After Markoff's arrest, Suffolk District Attorney Daniel Conley urged other victims to report any crimes by Markoff to police. Authorities also placed their own ad on Craigslist encouraging victims to come forward.
But as of Thursday, no one else had reported being a victim of Markoff's.
Authorities still hope that if Markoff did rob other people, those victims will come forward, but they realize that prostitutes and others who advertise erotic services through Craigslist may be reluctant to report a crime.
"This is a population of people who are not readily going to come forward," the official said.
Last week, investigators posted an item in the "erotic services" section of Craigslist asking, asking, "Were You Robbed After Using Craigslist?"
The ad said investigators believed that both women were attacked by a man "targeting female Craigslist advertisers who would be reluctant to report the crimes."
Markoff has pleaded not guilty.