A fourth person has been arrested on suspicion of modern day slavery amid allegations staff at two care homes were victims of the crime.
A 37-year-old woman from Rhymney, in Caerphilly, remains in police custody.
Gwent Police and the National Crime Agency executed warrants at Danygraig Nursing Home, in Newport, and Ashville Residential Care Home, in Brithdir, Caerphilly, on Thursday.
The three arrested previously have been released on conditional police bail.
They were a 53-year-old man and a 64-year-old man, both from Newport, and a 43-year-old man from Surrey.