Lexington Police last night arrested a Medford woman on prostitution charges after an officer responded to an online advertisement that said she would be working in the area.

According to a police report, Heather A. Lynch, 24, of 50 Water St., Medford, was arrested Thursday, Jan. 5 and charged with engaging in sex for a fee.

The arrest came after police responded to information that Lynch was advertising she would in town, Lt. James Barry, a spokesman for the Lexington Police Department, said Friday. 

Barry said LPD detectives routinely check the Internet for criminal activity in the area. In this case, a detective contacted Lynch, made arrangements and “developed probably cause enough to place her under arrest,” Barry said.

Lynch is the third alleged prostitute arrested in Lexington in the past year. The other two arrests occurred in June and July. The June arrest of a Boston woman allgedly working out of an apartment was also the result of an investigation that began on the Internet, while the July arrest of a transgender prostitute and escort came after a tip from hotel management.