An anti-slavery raid on a factory in Greater Manchester has uncovered workers from Eastern Europe allegedly paid under £2 an hour, police said.
Officers descended on the factory in Rochdale with teams from the council, Home Office and customs.
Three men, aged 51, 43 and 40, were arrested on suspicion of conspiracy to require another person to perform forced or compulsory labour.
A 24-year-old man was also held on suspicion of immigration offences.
The older men are also being quizzed over alleged trafficking offences.
Police claimed the raids "revealed a workforce of 20 Eastern European immigrants".
Det Insp James Faulkner, from Greater Manchester Police, said the factory was "producing frames and pictures for major high street companies".
However, neither the police nor Rochdale Council were able to give the BBC the name of the company that was raided, saying only it was a firm operating on Ings Lane in the town.
He added: "The men and women working in the factory have told us that they were subjected to physical and verbal assaults at the hands of their employers and forced to work more than 80-hours before ending up with around £25 for their week's work.
"This is a typical example of how modern slavery can work in the UK."
Police are investigating claims the workers had most of their wages - which Det Insp Faulkner said amounted to £125 per week - taken off them for "rent, travel and other expenses".