Residents and workers in parts of Brimbank and Melton have been put on alert after COVID-19 samples have been found in wastewater in Caroline Springs.
Health Minister Martin Foley said positive readings had been found in waste water in Caroline Springs from July 26 to 28.
He said residents who either live or work in Albanvale, Burnside, Burnside Heights, Caroline Springs, Deer Park, Delahey, Hillside, Keilor Downs, Kings Park, Plumpton, Sydenham, Taylors Hill and Taylors Lakes and have any symptoms are being encouraged to get tested.
The samples come as three new COVID-19 cases were announced in Victoria in the past 24 hours.
All three cases were in isolation throughout their infectious period and connected to known outbreaks.