Six prisons have been placed into total lockdown in Victoria after a staff member tested positive for coronavirus at the crowded facilities.
Corrections Victoria confirms a prison officer at Ravenhall Correctional Centre has contracted the virus and the facility is now in lockdown.
A further five prisons have also been placed in lockdown, including Hopkins Correctional Centre, Langi Kal Kal, Barwon Prison, Fulham and Loddon.
A Department of Justice and Community Safety spokesperson says the officer has been self-isolating since July 16 after being notified they were a close contact of a positive case.
The officer's contact with other staff and prisoners is being investigated and contact tracing is currently under way, with affected staff and prisoners being notified.
The latest case comes after a new prisoner at Metropolitan Remand Centre, also located in Ravenhall in Melbourne's west, tested positive last Friday.
The Victorian government is being urged to release Aboriginal and Torres Strait Islander inmates to prevent their deaths in custody due to COVID-19.
"COVID-19 positive prison officers who move in and out of prisons will place both people in prison and the wider community at risk," said National Aboriginal and Torres Strait Islander Legal Services co-chair Nerita Waight in a statement.
"The Victorian government must urgently and responsibly release at risk Aboriginal and Torres Strait Islander people from adult and youth prisons, due to our high vulnerability to severe and lethal impacts of COVID-19."
Greg Barns SC from the Australian Lawyers Alliance said selected prisoners needed to be released to avoid "a potential catastrophe".
"People in prison are at extreme risk of contracting the virus simply because they are detained. In our overcrowded prison system, social distancing is impossible and lockdowns create an increasingly intolerable and unstable environment.
"Non-violent prisoners, prisoners who are on remand simply because they have no home address, and vulnerable prisoners such as those over 65 should be released now," Mr Barns said in a statement.
All new prisoners are tested and required to spend 14 days in protective quarantine, regardless of their coronavirus risk, a Department of Justice and Community Safety spokesperson said.
This also includes screening and temperature checks for all staff and professional visitors prior to entering a facility, physically distancing wherever possible, increased hygiene standards and the use of personal protective equipment.