Victoria has recorded two new local COVID-19 cases as authorities scramble to find the source of the state's Delta strain cluster.
The Department of Health reported the cases along with six overseas acquired infections on Sunday, as Melbourne endures its second weekend of strict lockdown.
The eight total cases, from almost 30,000 tests, take the number of active infections in the state to 85.
It is not yet clear whether the two new infections are linked as Victorian contact tracers continue to try and to track down the source of another two "mystery" cases.
The couple, who have been infectious in the community, were among five new local cases reported in the state on Saturday.
One of the pair had been a regular visitor to Craigieburn Central shopping centre and came forward for testing as a result of health department efforts to test heavily in the area.
That person's partner is the other unlinked case and is a construction worker, which has prompted the closure of a Melbourne building site, affecting 170 workers who are now all considered primary close contacts.
"Seven positive cases entered the Craigieburn shopping centre on different days and contact tracers are working to ascertain the man's exact movements to see if they overlap with any of them," testing commander Jeroen Weimar said.
The other three cases recorded on Saturday were less concerning, authorities said, because they were all primary close contacts of confirmed cases and had been quarantining during their entire infectious period.
Among these three cases are two Delta strain cases - a child of a family already infected with the virus, and a family friend. That cluster appears separate to the rest of the Melbourne outbreak, which is made of the Kappa strain, which like the Delta strain has caused havoc in the UK and India.
Experts still don't know how the Delta strain entered the community and have been analysing genomic sequencing from across the country in the hope of finding a match.
Professor Sharon Lewin from Victoria's genomic sequencing centre, the Doherty Institute, said there was no evidence pointing to the Victorian family picking up the virus while on holiday in NSW.
Rather, her "strong hypothesis" is that it entered the community via hotel quarantine.
Melbourne is in its second week of strict lockdown and Health Minister Martin Foley has remained non-committal about guaranteeing restrictions will ease come June 10.