Victoria Premier Daniel Andrews has announced the state-wide lockdown will not be lifted as scheduled, saying the state is "not ready".
On Monday, Victoria reported 12 new Covid-19 cases, all linked to known clusters and four additional case identified on Monday which will be included in Tuesday's numbers.
There are over 15,000 close contacts which have been identified across the state, more than 250 exposure sites, including sites on Phillip Island in the south of the state to the Mallee district in the northwest.
"We are running alongside this virus but we are not yet out in front of it," the premier told reporters on Monday.
The premier likened the outbreak to a fire.
"We've got a containment line, we're making significant progress but it's not, it's not out yet," he said.
He said the state was not ready to get out of lockdown, though he said more details would be finalised on Tuesday, though he acknowledged Victorians might be "frustrated" and want a timeframe.
Testing figures, exposure sites and test results today will guide the extension, Mr Andrews said.
"We're trying to make sure we do this properly, and bring those cases to an end close off those changes community transmission, and then open with a sense of confidence that we can stay open," the premier said.
"I know this is not the news that people want to hear, but you got to do the right thing you've got this thing is moving so fast, it's so challenging."
All the new cases are linked to the current outbreaks of the Delta variant in the state, which originated in NSW and Mr Andrews said Victoria avoided a similar fate by going into lockdown.
"If we had been open, then we would be just like Sydney, we would have hundreds and hundreds and hundreds of cases," he said.
"We would not be looking at a short lockdown, we'd be looking at something entirely different."
Mr Andrews wished NSW well, after 98 Covid cases were recorded there on Monday, he added once NSW's Covid outbreak is under control, the pressure will be taken off other states.
When the lockdown was announced last week, Mr Andrews said there was a chance regional Victoria could come out of the lockdown before Melbourne, however on Monday he said doing so is "not safe".
"There is a threat across many different parts of the state," he said.
Among the cases is a household contact of the Mildura case revealed on Sunday, two are Trinity Grammar students, another is a close contact of a Phillip Island case, one is a case linked to AAMI Park and another was at the Euro 2020 viewing at Crafty Squire pub in the Melbourne CBD.
"That final case that Crafty Squire is of concern. It is absolutely an example of how quickly this variant is moving in the short time we are seeing between exposure and then being infectious and onward transmission," Chief Health Officer Brett Sutton told reporters.
"So while we acted as conservatively as possible in declaring Crafty Squire a high-risk venue, we didn't necessarily expect there to be transmission there. The fact it has occurred some 30 hours after being exposed is absolutely a feature of the Delta variant."
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