Virus fragments were found in a wastewater sample in Altona, and people in the area and surrounding suburbs have been urged to get tested.
The Department of Health and Human Services (PHHS) announced on Friday that the result was “unexpected given that it has been about eight weeks since the last known resident in the area had a coronavirus illness or diagnosis”.
Suburbs in the wastewater catchment include Altona, Altona Meadows, Laverton, Point Cook and Sanctuary Lakes.
People visiting Altona from 16 Monday through to 18 November should get tested if they have any symptoms “no matter how mild”.
More than 18,000 Victorians were tested in the past 24 hours, and the state now has two active cases.
Flights from New Zealand returned to Melbourne this week. As Victoria recorded its 21st day with zero cases on Friday, International flights are set to return to the state on 7 December but with a limit of 160 incoming passengers per day, who will need to isolate for 14 days. International arrivals from low-risk countries may be able to isolate at home rather than pay for a hotel.