Victoria has now recorded four new locally acquired COVID-19 cases over the previous 24 hours – including two new cases in aged care.

Those two cases, confirmed just before midday on Sunday, are linked to Arcare Maidstone, an aged-care facility in Melbourne’s inner west.

In a statement on Sunday morning, Arcare CEO Colin Singh confirmed a 79-year-old resident and an agency registered nurse who last worked at the residence on Saturday, had both tested positive.

The resident has had both doses of the Pfizer vaccine and is asymptomatic, but will be transferred to hospital as a precaution.

The nurse had received the first dose of the vaccine and is also asymptomatic.

All team members who worked at the facility on Saturday have been told to get tested immediately and self-isolate for 14 days.

The total number of cases in Victoria is down on the five locally acquired cases identified 24 hours earlier and a hopeful sign that stringent lockdown regulations in Melbourne are stemming the spread.

Meanwhile, authorities are scrambling 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 Melburnians endured their second weekend of strict lockdown.

The total of eight takes the number of active infections in the state to 85 as Victorian contact tracers continue their efforts to track down the source of two “mystery” cases involving a  couple known to have been infectious in the community.

One of the pair had been a regular visitor to Craigieburn Central shopping centre and came forward for testing as a result of a Health Department testing blitz in the area.

That person’s partner, the other unlinked case, 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.

Delta’s spread

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 from the rest of the Melbourne outbreak, which is made of the Kappa strain that has sown death and 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.

There are now 390 sites where exposure to the virus may have occurred and they can be viewed at coronavirus.vic.gov.au/exposure-sites.

The Victorian vaccine rollout is ramping up with the state to receive an extra 100,000 Pfizer doses from mid-June.

Paramedics will be the next frontline group to be prioritised for vaccination from June 9.

-with AAP