Merseyside police have raided 16 addresses as part of a crackdown on security firms operating protection rackets on sites in the Liverpool area.
Eleven arrests have been made in connection with theft, possession of stolen property and drug offences.
Police officers working with the Security Industry Authority and the Department for Work and Pensions have also visited more than 60 construction sites to check that firms providing security services are legally entitled to carry them out.
Chief superintendent Andy Cooke said the operation was linked to the regeneration of the city. He said: “Liverpool is continuing to benefit from a wealth of investment into the area in the run up to the Capital of Culture Year in 2008 and Merseyside police cannot stand by and watch rogue security firms benefit financially from the city’s regeneration.”