The Department of Health is yet to reveal detailed information on the detections.

But acting premier James Merlino has highlighted the need to retest people already in lockdown as the state prepares for restrictions to ease in regional areas.

"The public health team will work their hardest over the next 24 hours to make sure we have all the information we need to proceed with the easing of restrictions in regional Victoria from 11.59pm tomorrow night," he told reporters on Wednesday.

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Health minister Martin Foley said COVID-19 fragments were found during routine wastewater testing covering May 27 and 28.

The Department of Health is expected to circulate more information about the tests later today, which could help explain why previous testing in and around the same period has not appeared to pick up the fragments earlier.

At the time of this story's initial web publication at 2.20pm on Wednesday, multiple pages of the department's website said that there were no detections over the period, including on May 26, 27, 28 and 29.

Bendigo Health chief executive Peter Faulkner said it was important people did not panic but said testing centres were open for people displaying even the slightest symptoms.

"Extending hours of testing centre to 6.30pm tonight and we'll monitor that on a day-by-day basis," he said.

"We have reached out directly to the primary close contacts of the COVID-positive case that was in Bendigo last weekend and for those in the affected postcode areas - of which there are 27 - they have all been contacted and asked in for re-testing, just out of an abundance of caution.

"For the remaining 60 primary close contacts. We've messaged them and suggested they also come and get tested but they weren't in the postcodes identified by the wastewater detection program."

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The retesting program could provide clues about whether the positive tests were of someone who did not have an active COVID-19 case but could be virus shedding, Mr Faulkner said.

Bendigo and Axedale are not the only places where unexpected wastewater detections have been found.

Mr Foley revealed on Wednesday that another case surfaced in the Mornington Peninsula between May 27 and 31.

"We are working through those possibilities with our public health team, but the advice to members of the community in those particular areas is if you have any symptoms and if you particularly live in these areas, please get tested now," he said.

"That's the best thing you can do for yourself, for your family and to make a contribution to get these restrictions that are keeping us all safe done and dusted as soon as we can."

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