The police on Saturday arrested four women for suspected involvement in vice-related activities at a shop which offered facial services as a front.
The four, aged 27 to 33, were nabbed during a raid at the shop along Upper Serangoon Road. Transaction records and cash amounting to $1455 were also seized.
The shop's male owner was arrested as well. Another man was also arrested for possessing obscene material.
Preliminary investigations showed that illicit activities, which potential customers could book, were advertised in newspapers and online forums. Investigations are ongoing.
Anyone found guilty of knowingly living on the earnings made from another person's prostitution can be fined up to $10,000, jailed for up to five years, or both.
Any male person convicted of a second or subsequent such offence can also be caned.