Police have withdrawn more than 7500 speeding and red light tickets in Victoria after a computer virus forced a major investigation of the system.

The government and police say there will be no further tickets issued after cameras were compromised when a maintenance worker inadvertently uploaded a ransomware virus onto the network.

“I have decided to withdraw all infringements statewide. That does not mean they won’t be reissued, but I need to be absolutely sure that the 280 cameras were working correctly and without any corruption,” Assistant Commissioner Doug Fryer said on Saturday.

“I’d anticipate that all infringements detected between the sixth and the 22nd of June would exceed probably 7500 tickets.”

The government has launched an investigation of the system which is expected to take a number of weeks.

“Last evening I was notified that there had been 42 other cameras that had also been infected,” Police Minister Lisa Neville told reporters on Saturday.

“At no point could I be confident that this virus had not gone into any other of the 280 cameras.”

Ms Neville said she only heard about the breach in the media and has had discussions with the Department of Justice about the lack of communication.

The contractors that operate the cameras, including Redflex, were slow to notify the Department of Justice and will be subject to rigorous reviews of their systems and governance, the minister says.

On Friday, police said 55 speed and red-light cameras across Victoria were found to have been infected with a cyber virus – but on Saturday the government quarantined the entire system statewide.

Police say once the review of the cameras has been completed, tickets will either be reissued or cancelled depending on the outcome.

Cameras are still in operation during the investigation and any people caught during this time may still have fines issued at a later date, police say.

Victoria’s Road Safety Commissioner John Voyage told AAP on Thursday the virus tried to take over the cameras but it was unable to do that because it couldn’t connect to the internet.

-AAP