Victoria's health authorities are concerned about two new cases of Covid-19 carrying the highly-infectious Delta variant of the virus.
The state reported five new cases of community-transmitted coronavirus on Saturday.
Victoria's Department of Health testing chief Jeroen Weimar told reporters two of the new cases have the Delta variant of Covid-19 also known as B.1.617.2.
Mr Weimer added the cluster of Delta cases now sits at nine and authorities are "most concerned" about it.
"So we have two families of four, both active with Covid, and then one where the primary close contact, workplace contact of the first case that was identified a few days ago," Mr Weimar said.
The family visited a number of areas in southern NSW last month while on holiday. On Saturday, the NSW Health department included Foodworks at Gundagai as a possible exposure site.
Anyone with symptoms who visited the supermarket on May 19 between 11am-12pm is being encouraged to present for testing.
The latest outbreak now has 70 attached cases with one who has since recovered.
Questions over two shopping centre cases
Two more unlinked cases are believed to be attached to known exposure sites Craigieburn Central and Epping Plaza shopping centres.
Chief Health Officer Professor Brett Sutton told reporters authorities "have not got a definitive crossover time with known cases".
"But they did get tested, or at least one of them was prompted to get tested because they saw that we had concerns about those settings as potentially at risk for people who pass and have casual contact with others at,” Professor Sutton said.
Mr Weimar added authorities do have a theory on how the Craigieburn shopping centre visitor got sick.
"This individual is a daily visitor to Craigieburn shopping centre,” Mr Weimar said.
"We have now a total of seven positive cases on a number of different days, have been entered out of Craigieburn shopping centre and individual stores within there.
“That is a leading light of our investigation.”
Mr Weimar said there are now four active clusters across Melbourne.
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