Officers from the Simi Valley Police Department's Special Operation Unit conducted the sting operation last Thursday at three locations: Pacific Health on 1910 Hubbard St., Dream Tree Spa at 2515 Royal Ave., and W&H Massage at 1784 Erringer Rd.
Investigators said the businesses were advertised on websites as places where illicit sexual acts were performed in exchange for money.
Police identified those arrested as 52-year-old Linda Jiang, 46-year-old Aiqing Ding, 52-year-old Zi Fen Xu and 52-year-old Chun Lan Liu.
West Coast Massage on 1790 Los Angeles Ave. is also being investigated as part of an ongoing investigation, according to officials.
Police said they will continue to monitor local massage establishments for illegal activities. They said people who frequent massage locations for the purpose of engaging in illicit sexual activity will also be subject to arrest and prosecution.
Anyone with information about these massage businesses or other locations were asked to contact police at (805) 583-6950.