Victorian authorities are considering stricter lockdowns as numbers of untraceable "mystery" COVID-19 cases rise.
The state's number of confirmed infections rose by 397 on Saturday, and although this was far fewer than Thursday's peak of 723 Premier Daniel Andrews was not encouraged.
The state government's cabinet crisis committee is believed to have held a teleconference overnight, with a view to Mr Andrews announcing new and tougher restrictions on Sunday or Monday.
Melbourne and Mitchell Shire could be facing a six-week period of tighter constraints, including the almost complete shutdown of the city's public transport network, starting from Wednesday.
Residents could be limited in the distance they can travel from their homes and businesses selling non-essential goods could be ordered to close under a stage four lockdown.
Among the latest list of infections in the state are 49 cases with no known source, bringing suspected community transmission to nearly 2000 cases.
"We can't be certain there's not even further community transmission, even more mystery cases out there," Mr Andrews said on Saturday.
"That is in some respect our biggest challenge."
Australian Medical Association President Tony Bartone said this week Stage Four restrictions may be the only way to have an impact influential enough to bring down rates of community transmission.
“By calling for severer restrictions and calling for a ‘stage four’... that will then get a message out that this is really serious and reduce the movement in our community,” Dr Bartone told ABC Radio.
Victoria's Chief Health Officer Brett Sutton said there were discussions being had about the prospect of further restrictions like New Zealand has had, requiring the shutdown of all non-essential services.
The premier has been frustrated by people disobeying public health orders, including positive cases who weren't home when defence force members came knocking.
One person was fined on Saturday for leaving Melbourne to drive to Wodonga for a McDonald’s Big Mac, while another tried to drive from Werribee to Springvale - opposite sides of Melbourne - for groceries.
Mr Andrews said the time for warnings had passed and a "much bigger fine" through the courts is being considered as an alternative to on-the-spot fines.
The aged care crisis continues in Victoria with 1008 active cases currently linked to the sector.
Meanwhile, a group of Victorian teachers and parents has written an open letter asking Professor Sutton to reconsider his health advice about schools continuing to remain open.
"We see no medical or public health grounds why your advice to everyone in Victoria that 'if you can work from home you must work from home'...should not also apply to school staff at this time of extensive community transmission of the virus," the letter read.
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