A coworker of a Melbourne man who tested positive for Covid-19 after attending a super-spreader gathering in Sydney has also caught the virus.
Health authorities on Thursday evening confirmed the second positive case, a man who works at a dry-cleaning business in the suburb of Sandringham.
"His family has been isolated and are being tested, and urgent public health actions are underway to understand the case's movements," Victoria's Health Department said in a statement.
The business has been closed for deep cleaning and QR code data is being analysed to determine the movements and close contacts of the new case.
Earlier on Thursday, authorities revealed the first case, a man from Oakleigh aged in his 60s, had returned a positive test after returning to Melbourne from Sydney.
The pair were the only close contacts at the dry cleaning business, the health department says.
The Oakleigh man was one of about 30 guests attending a birthday party at his daughter's house in West Hoxton in Sydney on Saturday night.
He developed symptoms on Tuesday at his apartment complex home, which is currently the subject of a health department risk assessment, before he was tested on Wednesday.
"My understanding at this point is that he's not yet being contacted by NSW's contact tracing team," Victoria's COVID commander Jeroen Weimar told reporters on Thursday afternoon.
"The reasons for that we'll work through in the coming hours."
Airport listed as tier one exposure site
The Oakleigh man was aboard a return flight from Sydney Airport on Sunday afternoon.
The JQ523 Jetstar flight and terminal four of Melbourne Airport have been listed as tier one exposure sites, as has the dry cleaning shop.
"There are two people who work in that establishment, and there will have been customer contact," Mr Weimar said.
Authorities are also tracking down those aboard the flight from Sydney.
Victorian health authorities believe the man likely has the more infectious Delta variant, which has been circulating amid the growing Bondi cluster.
Health Minister Martin Foley said there was no suggestion the man breached any permit regulations, as West Hoxton was classed a green zone over the weekend.
It is unclear whether he is partially or fully vaccinated, though officials praised the man for immediately coming forward for testing.
In light of Sydney's worsening outbreak, Victoria will make Greater Sydney, the Central Coast, Shellharbour, Blue Mountains and Wollongong "red zones" under the state's permit system from 1am on Friday.
Air passengers are still able to fly out from Sydney Airport as long as they have not visited any red zone areas.
But Mr Foley issued a stern warning for non-Victorian residents, with at least six put back on return flights to Sydney on Wednesday after arriving from banned areas without a permit.
"If you try to enter Victoria through the airport you can be fined and you will be sent back," he said.
Patrols are being ramped up along road borders across the Murray River as well, with police scanning number plates to identify potential Sydneysiders.
Despite the new Sydney-linked scare, Mr Merlino confirmed Victoria would proceed with the planned wholesale easing of Covid-19 restrictions from 11.59pm on Thursday.
Victoria had earlier reported one new case over the 24 hours to midnight on Thursday among a primary close contact linked to the outbreak at the Kings Park apartment complex in Southbank.
The man has been quarantining throughout his infectious period.
Another three new infections were detected among returned travellers in hotel quarantine, raising the state's active case to 52.
Over the same 24-hour period, some 22,800 test results were processed and 17,800 Victorians received a vaccine dose at state-run hubs.
Meanwhile, Treasurer Tim Pallas has revealed Victoria's economy took a $1.3 billion hit during its fourth lockdown.
Treasury estimates the first week of lockdown, which encompassed all of Victoria, cost $700 million, while the second week in metropolitan Melbourne cost $600 million.
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