On Wednesday officers targeted a number of businesses in order to identify victims of human trafficking and to arrest those responsible for their exploitation.
At one car wash they found poor working conditions, unsanitary living areas and evidence staff were being paid below the minimum wage.
Three men, aged 28, 29 and 38 were arrested. They have since been bailed pending further inquiries.
Detective Sergeant Ash Turner from the force’s safeguarding intelligence team led the operation. He said: “Yesterday’s activity was a success and gave us more evidence that human trafficking and modern slavery is happening in this county.
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“We found people working in a seemingly legitimate car wash which was in reality being used to exploit foreign nationals.
“The six people we safeguarded yesterday are being given the appropriate help and support from the Red Cross and Salvation Army who we work alongside.
“We know there are people being kept in slavery in this county and we need the public to be aware of the signs to look out for which may indicate somebody is a victim and to let us know if they have any suspicions.
“This is a complex area of criminality which we are only just beginning to understand and it is often hidden in plain sight.”
For help and advice visit www.modernslavery.co.uk or call the helpline number 0800 0121 700
To report call 101 or call Northamptonshire Police on 101.
In an emergency always call 999.