Four people have been arrested in Cardiff accused of a string of offences including kidnapping, forced labour and slavery.
Gwent Police officers working under Operation Imperial arrested four men from the Rumney area of the city following raids on five addresses in the Welsh capital and Bristol.
A 57-year-old man, a 37-year-old man and a 33-year-old man, all from Rumney, were arrested on suspicion of kidnapping, knowingly or conspiring to hold a person in slavery, servitude or requiring another person to perform forced or compulsory labour, false imprisonment and assault.
A 34-year-old man from Rumney was arrested on suspicion of knowingly or conspiring to hold a person in slavery, servitude or requiring another person to perform forced or compulsory labour and assault.
The investigation also involved officers from South Wales Police and Avon and Somerset Police.
Det supt Paul Griffiths, who leads Operation Imperial, said: "The alleged offences we are investigating are extremely serious and we would urge anyone with any information which could assist to contact the Imperial team directly by dialling 01633 647 17401633 647 174.
"Alternatively if someone has information and would rather not pass this directly to the Police then I would urge them to contact Crimestoppers, which is independent of the Police and guarantees complete anonymity on 0800 555 1110800 555 111."