Victoria has recorded one new local COVID-19 case as contact tracers race to ring-fence an outbreak of the infectious UK strain.
There are 14 cases of the infectious UK variant of coronavirus linked to the Holiday Inn as the entire state undergoes a five-day "circuit-breaker" lockdown.
Premier Daniel Andrews said on Saturday there were 996 known primary close contacts associated with the known cases with test results expected to come through by Monday.
The single additional positive case recorded on Saturday - a man in his 30s - is in isolation, as well as 38 of his primary close contacts.
Of 12 co-workers of an infected worker at Brunetti's cafe at Melbourne airport, 11 have returned negative test results, which the premier said was encouraging. The one remaining test result is yet to come through.
Mr Andrews defended the need for a third lockdown, saying he knew a lot of people would be hurting but that it was the right thing to do.
"Victorians know what has to be done, we've done it before. I know it's not easy," he said.
"No one wants to make these sorts of decisions but when you have advice then you have no choice."
The outbreak can be traced back to a family of three who quarantined at the Holiday Inn and are believed to have been infected overseas.
One family member, who is in intensive care, used a medical device called a nebuliser in their room despite them banned outside of medi-hotels.
Mr Andrews brushed off reporters' questions about the nebuliser on Saturday, deferring to COVID-19 Quarantine Victoria commissioner Emma Cassar who is expected to speak to media later in the day.
It followed Mr Andrews' comments on Friday that it was clear nebulisers were not allowed, contradicting the man own's account given to the The Age that quarantine staff had let him use it.
Five international flights that were in transit when the Victorian government announced a pause on all passenger arrivals will arrive in Melbourne on Saturday, amounting to about 100 passengers.
Until 11:59pm on Wednesday, Victorians are only able to leave home to shop for food and essential items, provide or receive care, exercise and to work or study if they can't from home.
The rules are largely in line with stage-four restrictions imposed last year, with a five-kilometre travel limit, compulsory face mask usage and no visitors.
The premier is confident the lockdown - similar to what was imposed in Adelaide, Brisbane and Perth after cases escaped quarantine - would work.
Authorities are tracking down 5000 people who passed through Melbourne Airport's Terminal 4 after a case worked at Brunetti cafe while infectious on February 9 between 4.45am and 1.15pm.
About 29 flights arrived and departed through the terminal during that window.
Anyone who visited the terminal then needs to get a test and isolate for 14 days, including those who have since travelled interstate.
Victorian health authorities revealed new exposure sites on Friday evening including the Coates Hire Werribee and Caltex Woolworths in Hoppers Crossing as well as the Craigieburn train line, the 513 Eltham to Glenroy bus route and the 901 Frankston to Melbourne Airport bus route.
Victorian opposition leader Michael O'Brien said Victorians have every right to be furious they are in lockdown for a third time.
