The security breach - detailed in an internal Victoria Police dossier - is among two dozen cases of people gaining unauthorised access to secure areas of police stations and buildings statewide.

Released to Fairfax Media under Freedom of Information laws, the 2015 security incident register also details a potentially "catastrophic" breach involving a mentally ill man, an attempted safe break-in and a burglary in which thieves stole a police gun.

It does not include the unsolved firebombing of Pakenham police station in March in which a balaclava-clad man threw a molotov cocktail through the front doors of the complex.

The log shows that in August last year a male guard from Wilson Security, who was hired to patrol the Victoria Police Academy in Melbourne's south-east, gained unauthorised access to a female employee's bedroom.

It said the guard had "no permission or authority" to enter the Glen Waverley building or the woman's bedroom, and that he was subsequently removed from duty at the premises.

Millions of dollars was spent last year hiring armed security guards to protect key police sites, including the training complex, after the national terrorism public alert level was increased to "high".

Victoria Police spokeswoman Anthoula​ Moutis said the guard no longer worked at the academy following a complaint about his conduct, but said "no criminal offence was detected".

Wilson Security spokesman Nick Tyrrell said a break-in had not been reported but refused to provide any details about the incident or why the guard was subsequently removed from the academy. "Wilson Security takes its responsibility to all clients, including Victoria Police, very seriously," Mr Tyrrell said.

The police log shows that in a case that posed a "catastrophic" risk in May last year, a man believed to be mentally ill reversed a vehicle into a compound behind a police station in Melbourne's northern suburbs.

Details of the incident are heavily redacted but police said the risk was elevated due to the possibility of "fatal or severe injury to others". Records show the man was apprehended after a police chase and that a security review of the station was ordered after the breach.

In another incident, in rural Victoria, a police-owned portable classroom at a pistol club was burgled last August. Thieves got away with a non-working gun, police torches and other equipment. Records indicate the stolen property was recovered a month later.

The register shows that about a third of the security breaches in Victoria occurred in police station car parks, including two separate cases of vandals targeting officer's private cars while they were out on patrol.

The log shows a person was arrested after climbing through the window of a police building in the city and that someone stole a barbecue from a rural station. There were also cases involving people jumping the counters in the foyers of police stations, smashing a glass door and attempting to break into a safe.

Prior to 2014, Victoria Police did not maintain a record of unauthorised access to police facilities. Last year was the first full year that data was recorded. The location of the police stations where security breaches occurred was redacted for security reasons.