Fragments of Covid-19 have been found in sewage water in 31 Melbourne suburbs despite no community cases of the virus in Victoria in nearly two months.
The updated alert on Tuesday night urged anyone living in the suburbs in northern and eastern Melbourne to monitor for symptoms of the virus.
Victoria's last locally acquired case was 53 days ago.
Health officials said the sewage samples were either due to a positive case shedding Covid-19 in the early stages of an infection or when they are no longer contagious.
Residents living in northern and eastern Melbourne have been told to monitor for symptoms of Covid-19 after fragments of the virus were found in sewage water (file image)
'While it is possible that these detections are due to a visitor or visitors to these areas who are not infectious, a cautious approach is being taken,' Victoria's chief health officer Brett Sutton said.
Among the northern suburbs are Ascot Vale, Brunswick, Brunswick West, Coburg, Essendon and Essendon Fields.
In the east, the suburbs on alert include Bayswater, Bayswater North, Boronia, Croydon, Croydon North, Croydon South.
Victoria from Wednesday has opened three mass vaccination hubs to people over the age of 70.
From Wednesday, the Royal Exhibition Building, Melbourne Convention and Exhibition Centre and Geelong's former Ford factory will provide shots for anyone over 70 with or without bookings as part of phase 1a and 1b of the rollout.
'This is one way that we can expedite the vaccine rollout, as quickly as possible, particularly to our most vulnerable cohort,' Acting Premier James Merlino told reporters on Tuesday.
MELBOURNE SUBURBS ON COVID-19 ALERT
Pascoe Vale South
They will only be offered the AstraZeneca jab, with Pfizer doses still prioritised for healthcare workers under 50 at hospital vaccination clinics.
Despite concerns about the potential side effects, Mr Merlino said there had been an uptick in calls to the health department from older Victorians wanting to have the AstraZeneca jab.
'I see that as a positive sign,' he said.
More to come