A Brighton woman was allegedly sexually assaulted after replying to a Gumtree post advertising massages.
Police are appealing for anyone who has used the Pink Lady Massage Service to contact them after the 28-year-old invited the masseur to her Brighton home, where he is accused of sexually assaulting her during the hour-long treatment.
The Gumtree advert offered discounted massages for women only, a Sussex Police spokesman said.
The offence took place on November 21 and a 34-year-old man was arrested last month, a force spokesman said.
He has been released on conditional bail until January 24 and Gumtree has blocked the man from placing any future adverts.
Detective Constable Leon Ryan said: "I would remind people to be careful when inviting strangers into their homes in circumstances like this.
"If you are seeing someone for the first time, have someone else at home if possible.
"Agree what the treatment will involve beforehand and don't be afraid to ask them to stop if you feel uncomfortable."
Police are seeking anyone who has used or communicated with the Brighton-based service to call them on 101, quoting serial 0962 of 22/11, or by emailing email@example.com.