Victorian authorities are hopeful more genomic testing can shed light on how a Melbourne testing site worker caught COVID-19.
Initial genomic results have linked the case back to the outbreak at Maribyrnong's Ariele apartment complex sparked by a crew of NSW removalists, two of whom later tested positive.
But it has not been able to directly establish an origin for the Frankston man's infection with the Delta strain.
Health Minister Martin Foley confirmed further genomic testing was underway to find the missing link between him and known cases.
"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," he told reporters on Friday.
Most of the man's Mooney Valley testing site colleagues have so far returned negative results, 48 out of 58 workers, 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. All residents are currently in isolation as testing at the building continues on Friday.
Health department Deputy Secretary Kate Matson said the complex would not be listed as an exposure site, but warned people to keep an eye on the website as other sites may be added later on Friday.
It comes as Victoria recorded three new local COVID-19 cases on Friday from over 43,500 test results, including a previously reported infection.
Two cases are linked to existing outbreaks at Bacchus Marsh Grammar and Trinity College, while the other is linked to a Richmond apartment complex. All were in isolation for their entire infectious period.
Despite it being the state's lowest daily case figure since the outbreak began two weeks ago, Mr Foley warned Victoria was not out of the woods.
"We're not there yet," he said.
"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."
It will soon be one year since Victoria recorded its highest daily COVID-19 case total - 725 on August 5.
Reflecting on the upcoming anniversary as NSW battles its own major outbreak, Mr Foley described it 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.
There are now 200 active cases in Victoria, down five from Thursday, with six cases in hospital including two in ICU and one requiring a ventilator.
Some 4200 close contacts were also cleared to leave isolation, taking the number released in the past three days to more than 10,000.
In addition to a previously announced positive wastewater sample in Camberwell, another has been found this week near Caroline Springs in Melbourne's outer west.
Residents of Caroline Springs and 11 neighbouring suburbs have been urged to come forward for testing if they have symptoms.
Australian Associated Press