The possibility of stage four restrictions in regional areas - prompted by rising coronavirus numbers in Bendigo and Ballarat - could also be introduced in other areas like the North East, the Victorian Premier has warned.
Daniel Andrews told regional media on Friday that even if the numbers say the North East has no cases, the rise in "mystery cases" across Victoria means the government can no longer be sure.
One in five metropolitan cases, and 13 per cent in the regions, cannot be traced back to a confirmed source.
"I know some of your readers might say 'we've got stage three and we've got no case numbers' - no cases that we know of, that's the key issue. It's the mystery numbers that are of the greatest concern to us," Mr Andrews said.
He said the difficulty in waiting until cases rise to introduce restrictions was that there is a 10 to 14 day lag on seeing the benefits.
"If you wait, it can get away from you and then you haven't got a chance. You're then chasing rather than trying to stay ahead of that," he said.
"I do hope not to get to this at all, but I can't guarantee that."
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Facing multiple questions about the possibility of stage four restrictions, Mr Andrews said regional areas were not yet at that point.
"We are doing everything we possibly can to avoid having to put any additional rules in place," he said.
"It would only be if we thought case numbers were set to take off that we would impose additional measures and we would try to make those as proportionate and balanced as possible, because we know how much pain and loss is associated with some of those changes.
"It will be directed where the problem is, if we get to that point."
The Premier also addressed the issue of locum doctors not being able to travel from Melbourne across the border to Albury hospital, saying he would look into a solution.
"If there are arrangements we can put in place ... where people might be able to come and stay, so there is very low risk, or move within a bubble that might include Wang for instance, I'm more than happy to do that," he said.
He was less willing to get involved in his home town of Wangaratta pushing to host the AFL grand final.
"That would be an act of such parochialism as to betray my responsibilities to the entire state," Mr Andrews said.
Benambra MP Bill Tilley has been among those critical that the border around Melbourne is not hard enough to stop people travelling to the North East.
"I certainly wouldn't rule out further steps about trying to curtail movement," Mr Andrews said.
"If people are making steps that are not absolutely necessary, then there is a risk that they can bring the virus with them and not even know."