Authorities are meanwhile hopeful more genomic testing will shed light on how a Melbourne testing site worker caught COVID-19.
Initial results have linked the case to the outbreak at Maribyrnong's Ariele apartment complex sparked by a crew of NSW removalists.
But so far no origin for the Frankston man's infection with the Delta strain has been established.
"What we're missing at the moment is a link between this gentleman and his source of acquisition, and we're working hard to track that down," Health Minister Martin Foley told reporters on Friday.
Some 48 of the man's 58 Mooney Valley testing site colleagues have so far returned negative results but Mr Foley said work and social contacts remained the best prospect for finding a source.
The worker, who was not believed to have been vaccinated, also visited his partner at a Newport apartment building while infectious.
Health department Deputy Secretary Kate Matson said that premises would not be listed as an exposure site but warned people to keep an eye on the website as other sites may be added.
Victoria recorded three new local virus cases on Friday including a previously reported infection.
Two cases were linked to existing outbreaks at Bacchus Marsh Grammar and Trinity College, while the other was traced to a Richmond apartment complex. All were in isolation for their entire infectious period.
Despite it being the state's lowest daily figure since the outbreak began two weeks ago, Mr Foley warned Victoria was not out of the woods.
"There is still evidence of transmission out there in the community and we need to continue to follow the public health rules to make sure that we can stay open and stay safe," he said.
Thursday marks one year since Victoria recorded its highest daily COVID-19 case total - 725.
As NSW battles its own major outbreak, Mr Foley described the occasion as a "bitter" and "painful" experience.
"The huge loss that so many Victorians endured this time last year has burnt deeply into our psyche, has burned deeply into our public health response," he said.
As of Friday, there were 200 active cases in Victoria, with six in hospital including two in ICU and one requiring a ventilator.