Four people have been arrested by a team of 100 police officers conducting an inquiry into slavery and servitude.
An Eastern European man has been taken to hospital after the raids in Cardiff, Monmouthshire and Marshfield.
The inquiry was sparked by the discovery of another man found living in poor conditions in Marshfield earlier this year.
Officers have also said they are investigating if a body has been buried at a farm in Marshfield.
The four arrested - a 66-year-old man and a 42 year old both from the Marshfield area, a 36-year-old man from the Cardiff area and a 42-year-old woman from Penhow, Monmouthshire - are being questioned.
A man was taken from the Marshfield site for hospital treatment where his physical and mental condition is being assessed.