Four men arrested and held at Ystrad Mynach Police Station on slavery and kidnap charges have been released on bail.
Homes in the Rumney area of Cardiff and Bristol were raided by police on Monday.
The four were questioned at Ystrad Mynach for alleged offences which spanned 26 years.
Three men – aged 57, 37 and 33 – were held on suspicion of knowingly or conspiring to hold a person in slavery, servitude or requiring another person to perform forced or compulsory labour, kidnap, false imprisonment and assault.
A fourth man, 34, 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 allegations relate to two men, who police said were safe and being supported by officers. Police said the two alleged victims were not recovered from the addresses raided.
All four were released on police bail on Monday night.
The arrests were made by officers working on the anti-slavery Operation Imperial.