LONDON (Reuters) - British police who discovered a suspected slave labor operation on a caravan site north of London said they were questioning four people on Monday.
Police said they found 24 British and eastern European men living in "shockingly filthy and cramped" conditions on a travelers' site in Leighton Buzzard, Bedfordshire.
Some had been there for up to 15 years and, in the worst cases, lived in horseboxes, dog kennels and sheds, police said.
Four men and a woman were arrested on Sunday under a slavery act introduced last year after an operation involving more than 200 police officers, said the Bedfordshire and Hertfordshire Major Crime Unit. The woman was released on bail and will be questioned later, police said on Monday.
Many of the men found on the site appeared to have been recruited from soup kitchens for the homeless and benefits offices for the unemployed with the promise of an 80 pound daily wage, free food and lodgings, said police.
But officers said their investigation suggested the men had been held against their will and forced to work for no pay and little food.
Many were down on their luck, may have been alcoholics or had no family support, and were threatened with violence if they attempted to leave.
Some did escape and went to the police, with complaints dating back to 2008, police told journalists.
The force said the men rescued at the site included eight from Britain, three from Poland, a Lithuanian and a Latvian.
Local lawmaker Andrew Selous said questions had to be asked about the police, local authorities, and above all, those who used the alleged slave labor.
"Questions do need to be asked about the intelligence picture, who knew what, when and frankly why action wasn't taken before," the member of parliament for South West Bedfordshire told Sky News.
Detective Chief Inspector Sean O'Neil, from the Bedfordshire and Hertfordshire Major Crime Unit, said in a statement: "The men we found at the site were in a poor state of physical health and the conditions they were living in were shockingly filthy and cramped."
"We believe that some of them had been living and working there in a state of virtual slavery, some for just a few weeks and other for up to 15 years," he added.
(Reporting by Avril Ormsby; Editing by Andrew Heavens)