A major investigation is underway into a security breach in which a man allegedly posed as a police officer at the Perth Watch House.

The man has been arrested and charged but police are still investigating whether he managed to access any sensitive information.

It is understood an 18-year-old man was somehow able to get hold of a WA police uniform and impersonate an officer, turning up and carrying out work at the watch house in East Perth.

The man had a full police utility belt, complete with handcuffs, police issue baton and holster.

He was apparently able to work in the watch house unchallenged.

It is not clear if he had direct contact with prisoners or was able to access police computers while he was in the building.

The security violation was eventually detected but it sparked a major security scare with police initially believing the breach could be more widespread and involve a network of others.

It has been confirmed several police uniforms have been recovered from the man's residence, but some are believed to be still missing.

He is due to face court on a number of charges at a later date.

