Three people have been arrested on suspicion of modern slavery offences following raids.
Two properties in Greenacres, Oldham, Greater Manchester were raided and two potential victims were found.
A 66-year-old man was found and a man in his 50s from Hungary who alleges he was forced to work without wages for six years.
Two men aged 22 and 60 and a 23-year-old woman, all from Hungary, are being questioned.
The Gangmasters and Labour Abuse Authority (GLAA) and police launched an investigation following concerns about a man being driven to and from work at a food production factory.
One of the men found has been relocated after agreeing to enter the government's scheme for potential victims of trafficking.
Martin Plimmer, from the GLAA which works to protect vulnerable and exploited workers, said: "While we are still in the very early stages of this investigation we appear to have uncovered two victims - one of whom claims to have been exploited for a considerable period of time."