Victorians will stay confined to their homes after the state's five-day lockdown failed to stamp out an outbreak of the "wildly infectious" Delta coronavirus variant.
Premier Daniel Andrews has confirmed the lockdown will be extended beyond 11:59pm on Tuesday, after the state recorded four new local COVID-19 cases in addition to the 13 infections reported overnight.
"We are running alongside this virus, but we're not yet in front of it," he told reporters on Monday.
The premier said there were still "far too many" cases of community transmission for the statewide lockdown to lift as planned and it was impossible to ease restrictions earlier for regional communities.
"I don't want a situation where we fail to extinguish this, we fail to end these chains of transmission, only to open and then be closed again a short time thereafter," he said.
Victoria's public health team and senior government ministers will make the final call on the length of the extension by Tuesday morning.
Monday's testing figures and results, as well as any new exposure sites and mystery cases, will guide their decision.
The 13 new local infections recorded in the 24 hours to Monday morning are all linked to the current outbreak and include a man in the regional town of Mildura previously announced by authorities and his household contact.
Four people who dined at Ms Frankie in Cremorne have also tested positive as well as two Trinity Grammar students.
Other cases include a person who attended the Wallabies v France rugby match at AAMI Park, a close contact of the group of friends who went to Phillip Island, a Bacchus Marsh Grammar teacher and a patron of the Young and Jacksons pub in Melbourne.
Victoria's Chief Health Officer Brett Sutton is particularly concerned about the final case: a patron of the Crafty Squire, another Melbourne pub, which hosted a Euro 2020 soccer final event on July 12.
"It is absolutely an example of how quickly this variant is moving and the short time we're seeing between exposure and then being infectious," he said.
"Last year we would not have seen any circumstances where someone who had been exposed was transmitting to someone else a day and a half later."
The venue has been listed as a tier-one exposure site, with everyone at the event required to get tested immediately and quarantine for 14 days.
Professor Sutton said no other jurisdiction in the world has been able to keep up with the Delta variant.
"There is no absolute guarantee that we can win against Delta period, we have to give ourselves the absolute best chance, but we have to recognise just how profoundly challenging it is," he said.
"This will take off if we allow it to."
The four additional cases, which will be included in Tuesday's figures, are also linked to the outbreak but have been isolating throughout their infectious period.
The outbreak, which now totals 76 cases, originated from NSW.
There are now 15,800 close contacts and more than 280 exposure sites, including sites on Phillip Island in the south of the state to the Mallee district in the northwest.