Victoria has recorded 15 new coronavirus cases and one death, bringing the state's death toll to 807 and the national figure to 895.
The figures, confirmed by the Department of Health and Human Services on Tuesday, bring Melbourne's 14-day case average to 10.6, down from 11.6 on Monday.
Melbourne's total number of mystery cases between September 20 and October 3 is 13.
The city needs a 14-day average of fewer than five cases as well as less than five mystery cases before it can further ease restrictions.
When asked if Melbourne would meet the targets by October 19, Prof Sutton said: "My gut feeling is it will be a line ball. It's not certain one way or the other."
He said the state could move to the next stage if there are more than five mystery cases, depending on circumstances.
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"We'd have to see exactly where we were at, at that time including the trend. Because if all five of the cases are in the first week of that fortnight and we have seven or eight or nine days prior to the 19th that has absolutely no mystery cases, that's a positive," Prof Sutton said.
A case on Monday was linked to the Butcher Club and Chadstone Shopping Centre cluster, which now totals 24 people including nine family members, seven staff and three customers.
Three more sites have also been added to the state's high-risk locations list: Leo's Fine Food and Wine Supermarket in Glen Iris, Aldi in West Footscray and White Line Tyres in Benalla.
Anyone with symptoms is urged to get tested.
Australian Associated Press
