100 sites in Belfast, Lisburn, Southampton and Nottingham were visited as part of Operation Alexander, which was carried out to test compliance amongst operatives working in security roles.
SIA investigators checked 187 CCTV operatives, door supervisors, vehicle immobilisers and security guards.
The premises visited included shopping centres, universities, office blocks, retail parks, a ferry terminal and a job centre.
In Belfast and Lisburn, two operatives were detected working with Security Guarding licences that were not valid for the CCTV duties they were undertaking. The SIA is conducting further enquiries.
Investigators issued nine warnings to individuals for either failing to display the SIA licence whilst on duty or for not informing the SIA of a change of address.
Director of Compliance and Enforcement Dave Humphries said: “I am pleased with the results from these latest random compliance checks. We will continue to monitor compliance with SIA licensing requirements by carrying out further activities like this across the UK.
“I would like to remind licence holders that they must adhere to all conditions of the licence. For example, security staff must display their licence at all times while working, and must inform us if their address changes.”
* In Belfast and Lisburn, 87 operatives were checked. Three warnings were issued.
* In Southampton, 50 operatives were checked. Four warnings were issued.
* In Nottingham, 50 operatives were checked. Two warnings were issued.