Five people have been arrested on suspicion of people trafficking, money laundering and managing a brothel in Swindon.
Police went to an address in the Redhouse area of the town after receiving information, and arrested a woman and man, both aged 42.
Later, two women were arrested in Reading and a 29-year-old man was arrested in Bromsgrove.
They have all been released on police bail pending further inquiries.
The women arrested in Reading were also being questioned in relation to drugs offences, police said.
Det Sgt Emma Spooner, of Swindon CID, said: "Our enquiries in relation to this investigation are on-going and I would ask anyone who has any information that they feel could help our enquiry to contact the police."