Thousands of people who have travelled to New Zealand from Melbourne since 11 May will need to keep a close eye out for symptoms, Director-General of Health Ashley Bloomfield says.
Victoria's Department of Health had reported 10 new local cases in the 24 hours to midnight, and Acting Premier James Merlino revealed another case had been identified this morning.
It brings the cluster in Melbourne's north to 15.
New Zealand's quarantine-free travel bubble with Victoria has also been paused as a result of the community cases.
There are no new cases of Covid-19 in New Zealand today - either in the community or in managed isolation.
Bloomfield said more than 10,000 emails were sent out yesterday to people who have recently arrived from Melbourne over the past two weeks.
"It is very important that anyone who has been in Victoria since 11 May keeps a close eye on any development of symptoms."
He said people may be showing flu and cold symptoms as winter approaches, but anybody who had symptoms should not not go about their normal day, and should isolate, ring Healthline and go get a test.
There were 4776 tests processed in New Zealand yesterday.
In a statement, the Ministry of Health said it was possible that people from the Whittlesea local government area - where the cases were detected - in Melbourne may have been exposed to the virus and may now be in New Zealand.
The ministry is asking anyone who has been in that area to have a test five days after they were last in Whittlesea and stay in their accommodation until they have a negative test result, even if they do not have symptoms.
Victoria Health's up-to-date locations of interest is available online.
Bloomfield said ministry staff remained in close contact with their counterparts in Australia and they were keeping a close eye on the outbreak there.
Bloomfield said pausing quarantine-free travel last night was an appropriately precautionary response to keep Covid-19 out of New Zealand. It will be formally reviewed in 48 hours.
He said it is possible given the time between the case on 11 May in north Melbourne that there are undetected cases. He has asked anyone who has travelled from Melbourne or Australia or who has been in that area to be tested - at least five days since being in that area.