Coronavirus fragments have been detected in wastewater from Castlemaine, the Department of Health and Human Services revealed on Saturday afternoon.

Following the detection of COVID-19 fragments in Gisborne, Leongatha and Hamilton on Friday, DHHS has added Castlemaine, Pakenham and Cowes to its list of affected suburbs.

People who live in or have visited Castlemaine, Cowes, Hamilton and Pakenham between January 25 and 27 should remain alert for symptoms.

If you visited Gisborne between January 24 and 26 or Leongatha between January 17 and 19, DHHS advises you should also remain alert for symptoms.

Viral fragments in wastewater can be due to an active infectious case, but it can also be due to someone who has recovered from the virus and continues to shed it.

Wastewater testing will be increased to monitor trends in these areas and targeted testing may be implemented to help clarify the source, DHHS' website said.

Routine wastewater testing in December also detected COVID-19 fragments in Castlemaine on December 15.

Victoria has recorded no new locally acquired COVID-19 cases for a 24^th consecutive day.

The Department of Health and Human Services' daily update revealed one new internationally acquired case detected in the past 24 hours, which is being managed in the state's hotel quarantine system.

The number of active cases has reduced from 27 to 23 since Friday, as 13,702 test results were received.

On Friday afternoon, DHHS confirmed that fragments of the COVID-19 virus were recently found in wastewater at Gisborne.

There were also traces found at Hamilton, in western Victoria, and in the south Gippsland town of Leongatha.

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"Anyone who lives in or has visited Gisborne from 24 to 26 January, Hamilton from 25 to 27 January or Leongatha from 17 to 19 January, is urged to get tested if they have any symptoms of coronavirus (COVID-19), however mild," the department said.

Meanwhile, Victoria is allowing quarantine-free travel from all areas of NSW, with the elimination of "red zone" virus restrictions.

Red zones were eliminated from 6pm AEDT on Friday, with the area of Cumberland downgraded from a red zone to the only remaining orange zone.

According to Victoria's traffic-light system of travel restrictions, anyone travelling from Cumberland will have to self-isolate and get tested within 72 hours of arrival, remaining in isolation until they get a negative result.

All other parts of NSW will be designated green, which only requires travellers to get tested if they become symptomatic.

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