Slaves have been discovered living in dog kennels and horse boxes in a travellers' site in Leighton Buzzard.
Detectives are quizzing four men and a woman after the 24 slaves were discovered in what is being described as one of recent history's worst cases of slavery.
The five suspects, all living at the Greenacres travellers' site in Leighton Buzzard, are being detained on suspicion of slavery offenses.
It is believed that some of the men had been enslaved for as long as 15 years, being forced to work without pay and live in filthy conditions. Most of the men are from England and Eastern Europe.
Detective Chief Inspector Sean O'Neil, from the Bedfordshire and Hertfordshire major crime unit, told the Telegraph: ''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 others for up to 15 years.
''Because of the number of victims and suspects and the size of the site, we needed the assistance of many officers from specialist units today. We are aware the operation has caused a lot of disruption to the other residents of the site and we thank them for their co-operation and understanding.''