Stop-checks across Peterborough have taken place in a crackdown on illegal gang masters in the city.
About 120 people were stopped and 13 arrests made during Operation Dreadnought on Tuesday.
All the arrests were for immigration related offences such as employment of illegal workers and breaching of work permits, said a Cambs Police spokesman.
Police were also targeting benefit fraudsters and vehicle crimes by checking vehicles.
In total, eight vehicles were removed for driving related offences.
Officers were joined by the social security fraud investigation team.