The health authorities, who have been investigating the Delta cases in Victoria since last week, have yet to find a link with any other cases across Australia, reports Xinhua news agency.
Victoria's Acting Premier James Merlino said on Tuesday that a match had been made with a returned traveller who had entered hotel quarantine in the state capital of Melbourne on May 8.
"While we have a genomic link, we do not currently have an epidemiological link," Merlino said.
"There's currently no definitive understanding of where a transmission event may have occurred."
Investigations are continuing as to whether there was any contact between the returned traveller and those other Delta cases.
As of Tuesday, the state recorded two locally-acquired Covid cases of from 22,814 test results in the past 24 hours, both of which were linked to existing outbreaks, according to Merlino.
Overall there are now 92 active cases in the state, with 83 are locally acquired.
Merlino said the tracking down and isolating of cases meant that the lockdown was likely to be lifted on Thursday.
"We remain on track to later in this week announce further easing of restrictions in regional Victoria and careful easing of restrictions in Melbourne," he said.
Greater Melbourne's lockdown, which began on May 27, was extended for another seven days last Thursday, while regional Victoria's restrictions were eased.
"This cluster was discovered after the lockdown was in place and nothing about today changes our plan," Merlino said.