Victoria has recorded 92 new local covid-19 cases — the largest number of daily infections seen in the state this year.
Of those, only 61 have been linked to existing cases and outbreaks, meaning another 31 are mystery cases, state health authorities said on Sunday.
This follows 15 mystery cases on Saturday.
The state's sixth lockdown is scheduled to end on September 2. However, it is expected to be extended given the high number of mystery cases and people infectious in the community.
New cluster 'of some concern'
The news comes after health authorities announced on Saturday that a new cluster has cropped up in Port Melbourne. They are racing to link it to existing outbreaks and shut down chains of transmission.
Victoria has added 64 new Covid-19 infections to its caseload on Saturday, 28 of them involving community exposure.
They include four fresh cases in the Port Melbourne area, with exposure sites at a Fisherman's Bend supermarket and a car wash and auto warehouse.
The cluster is "of some concern", Covid response commander Jeroen Weimar said.
"We've not seen that crop up before, so we are very keen to make sure that doesn't become anything else."
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