More than half a million Melbourne residents have been put on alert after Covid-19 fragments were detected in wastewater in the city's north and southeast.
Victoria's Department of Health urged residents in the areas identified to watch for virus symptoms.
"The unexpected detections may be due to a person or persons with Covid-19 being in the early active infectious phase or it could be because they are continuing to shed the virus after the infectious period," a department update read.
In a new interactive map released by the department this week, the northern area marked in red indicates the affected area which stretches from Footscray in the inner-west to Macleod in the northeast, incorporating more than 60 suburbs, many of which are densely populated, including North Melbourne, Brunswick and Fitzroy.
Detections occurred on April 6 and April 12.
Wastewater in Cranbourne in the city's southeast, as well as its surrounding suburbs, has also identified virus fragments, also on April 12.
The combined population of the two areas identified surpasses 800,000.
Anyone from the affected areas or anyone who visited the identified suburbs with any symptoms of Covid-19, is being urged to get tested.
Melbourne 'Covid-free' for over a month
The state has not recorded a locally-acquired case since February 26 when two cases were linked to the Holiday Inn cluster sparked by a quarantine leak.
However, states were on alert after an outbreak in Brisbane at the end of March triggered a snap three-day lockdown in the city.
At the time Victoria slapped travel restrictions on those who had been in the Greater Brisbane area.
This week those restrictions were finally removed in full, with the region moving from an orange to a green zone, meaning people arriving from the area no longer need to isolate and wait for a negative Covid test result.
There are currently eight active cases in Victoria.
List of suburbs subject to latest Covid alert
Pascoe Vale South
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