Health Minister Martin Foley said two men, one woman and a child had been confirmed with the virus. All were close contacts, he said.

Earlier, the state’s Health Department was notified of the two probable cases on Monday morning.

“A full investigation is underway into these results, and initial public health actions are being put in place while both individuals isolate and are urgently retested,” the department said.

“We will communicate any specific public health actions the community needs to undertake as soon as possible when investigations and case interviews are complete.”

It comes after the department admitted it had listed the wrong supermarket as an exposure site during an outbreak earlier this month.

People had been warned of potential exposure at Woolworths in Epping a fortnight ago, after a Victorian man contracted coronavirus in hotel quarantine in South Australia.

But the department on Friday said the man had shopped at Woolworths in Epping North, three kilometres away.

Also on Friday, Victorian Chief Health Officer Brett Sutton warned there may be an “active but undiagnosed infectious case” in Melbourne’s north after traces were picked up in wastewater in the Epping and Wollert area on Thursday.

Transport Infrastructure Minister Jacinta Allan said the probable cases were being “thoroughly investigated”.

“It’s too soon to draw any conclusions about the connection between these two cases and previous cases,” she told reporters on Monday.

“The only advice I have is that they are connected to each other.

“We need to let the investigations and the interviews take place so we can provide a full and accurate picture to the Victorian community over the course of today.”

She urged any Victorian with symptoms to get tested and isolate until they receive a negative result.

Opposition Leader Michael O’Brien said it was clear the government had stuffed up contact tracing.

“If we get another outbreak in Melbourne because this government didn’t do the basics right then frankly, the health minister, and other ministers need to lose their jobs,” he said.

The cases brought Victoria’s 86-day run of no community transmission to an end.

Australia’s Chief Medical Officer Paul Kelly said they would be the first locally acquired cases in the nation for the last 13 days.

“It’s a stark reminder if you are on the list to get a vaccine, do not wait to get your vaccine,” he told reporters in Canberra.

“We are approaching winter very quickly. We’ve been in a very good position this year in terms of acquired cases in Australia but that can change very quickly.”

Having recently visited the UK, Victorian-based federal cabinet minister Dan Tehan said there were benefits to mass vaccination.

“They are, with confidence, looking to open their economy and their way of life,” he told Sky News.

Tehan said the Commonwealth would support Victorian efforts to deal with the two possible cases.