Officers with operatives from the Security Industry Authority (SIA) and Department for Work and Pensions targeted 10 security guards at the sites.
Six were found to be working without valid security licences and two were not displaying their licences.
SIA’s head of investigation Christy Hopkins said: “We will keep targeting security sites and keep the environment as hostile as possible for rogue security firms – we cannot let them have a strong hold in the security industry.
“By working together with our partners, we send a strong message that non-compliance with the law will not be tolerated.”
The operation was the latest in a series of raids aiming to crack down on security gangs with links to organised crime.
The SIA said the rouge security firms extorted money from builders, demanding contractors hire their security teams “or else”.
