Regional Victoria has been spared from new home and public gathering restrictions (as of Wednesday morning) imposed on greater Melbourne to contain the potential spread of the Whittlesea cluster.
The Victorian government could yet impose tighter restrictions on sports crowds and other mass gatherings if a COVID-19 cluster in Melbourne's north continues to grow.
One of the infected people in a growing coronavirus cluster in Melbourne's north attended an AFL match on the weekend, prompting a government health warning.
While the outbreak started in the northern suburbs, country Bendigo and Port Melbourne now feature among 43 exposure sites listed on the state health department's website - well up on Tuesday's 10.
The infected fan was at the Collingwood-Port Adelaide game at the MCG on Sunday May 23, sitting in Zone 4, Level 1 of the Great Southern Stand at the Punt Road end.
Spectators who sat in the same area are being contacted by Victoria's Health Department using data from tickets and QR codes. They will have to get tested and isolate until they test negative.
Others who sat in the surrounding area are being told to go for testing if they develop symptoms.
"Further reviews of CCTV footage will be undertaken to determine if the advice to test and isolate will be broadened beyond these areas," the department said in a tweet early on Wednesday morning.
Authorities sought to reassure people who attended the gaming, saying the AFL and MCC had "prepared for this situation in multiple simulations."
While COVID-19 restrictions were ramped up in Melbourne on Tuesday, more could be on the way as authorities panic about the cluster, which started at Whittlesea in the city's north.
The 43 exposure sites now include tier one locations in Coburg and Fitzroy, as well as Port Melbourne.
A bar at inner-suburban Prahran also posted on social media that it is now listed as a tier 1b exposure site.
The growing number of exposure sites and their locations show the virus potentially spreading well beyond Whittlesea and surrounding areas.
The cluster has grown to nine cases after four new infections - all household family contacts of a man in his 60s - were confirmed on Tuesday afternoon.
Victoria Chief Health Officer Brett Sutton warned there may be further cases in the next 24 hours, with 84 of 168 primary close contacts testing negative so far, telling ABC Radio Melbourne:
"We have to chase down every single close contact ... but it's certainly not out of control."
In response to the unfolding situation, restrictions have been imposed in the Greater Melbourne area with home gatherings limited to five visitors per day and public gatherings restricted to 30 people until at least June 4.
Masks are mandatory indoors for people 12 and over, but can be taken off for eating, drinking and exercise.
Schools and workplaces remain open, as are shops, cafes, restaurants and pubs and existing density limits apply.
Acting Premier James Merlino said:
"This is about giving our contact tracers the time that they need to track this matter down and get on top of it."
A public health advisory panel will soon decide if further restrictions are needed for large events including AFL games and the RISING festival, which is due to begin on Wednesday.
The Western Bulldogs have already had their weekly preparations interrupted, with the AFL club's players and staff forced into isolation after an employee attended an exposure site.
Pending negative test results being received overnight on Tuesday, the Bulldogs expected players and staff to return to training on Wednesday.
Genomic sequencing shows the outbreak is linked to the case of a Wollert man, who contracted the virus in South Australian quarantine earlier this month.
The man, in his 60s, could be the possible "source case" for the City of Whittlesea outbreak, although a definitive link is yet to be established.
Queensland, Western Australia and South Australia have all significantly tightened their borders to Victoria while stopping short of completely slamming them shut for most travellers.
A New South Wales health representative told FlowNews24 that people who were not NSW residents returning to the state would be stopped at the border if they had visited any of the nominated potential exposure sites.
-- with AAP