Victoria Police is on stand-by for enforcing stay at home orders if the Victorian government decides to implement a snap lockdown.
Deputy Commissioner Rick Nugent has confirmed he will meet with state government advisers at 11 am to be briefed on their plan for how to respond to the spike in coronavirus cases caused by a leak in the state's hotel quarantine system.
"I was chatting with the Chief Commissioner 15 minutes ago sort of thinking through what it might look like and what our role might be in that," he told radio station 3AW on Friday morning.
Senior cabinet ministers, the Premier, and public health officials met last night to consider how to respond to the outbreak, according to a state government source with knowledge of the talks, commenting on the condition of anonymity.
They said a final decision on whether to increase restrictions had not been reached, with authorities waiting on more testing data this morning before finalising their response.
Premier Daniel Andrews is expected to outline the government response at a press conference later this morning.
It comes after the cluster again swelled overnight, with another two people testing positive for COVID-19, bringing the total number of cases linked to the outbreak to 13. One of the cases spent more than eight hours at a busy airport cafe while infectious on Tuesday.
On Friday morning, Prime Minister Scott Morrison has weighed into the discussion, supporting calls for a "short-sharp" lockdown.
He told radio station 3AW that Health Minister Greg Hunt had been in touch with Victorian counterparts overnight and those discussions about the prospect of a lockdown are "underway".
When asked directly if he had been briefed there would definitely be a lockdown, Mr. Morrison said "not at this stage".
Victoria's Department of Health confirmed the two new cases in a tweet at 11 pm on Thursday night - stating that both are household primary contacts of previously announced cases.
Five cases in total were discovered on Thursday which was recorded in Friday's official numbers. There are now 19 active cases in total in Victoria, with over 24,000 tests conducted on Thursday.
Authorities confirmed on Thursday there were between 400 and 500 close contacts of confirmed cases.
There are no mystery cases in Victoria - it has been 37 days since the state had a case with no known source.
Brunetti cafe at Melbourne Aiport's Terminal 4 was added to the state's growing list of ‘Tier 1' exposure sites just after midnight on Thursday.
A newly confirmed positive case was at the cafe for more than eight hours from 4.45 am to 1.15 pm on Tuesday, February 9 while potentially infectious.
Melbourne airport confirmed 29 domestic flights arrived and departed Terminal 4 during that period, and a deep clean of the area was conducted overnight on Thursday in response to the news.
Anyone who visited the cafe or who worked during those times is being directed to isolate and test immediately and remain isolated for 14 days.
A clinical epidemiologist at the University of Melbourne Professor Nancy Baxter said Victorian authorities should be "thinking very hard" about implementing a snap lockdown to stem any unlinked transmission from the new cases.
"What I am concerned about is as the at-risk sites grow and grow, there is the potential there has been some kind of spread outside of that group of close contacts that is already in quarantine [and] it could be a week or more before we know it," she told Nine's Today program.
"Then there is that opportunity for spread throughout the community, under our very noses.
Professor Baxter said although some may see a short lockdown as an overreaction, it was better to do one sooner rather than later.
"It is a very tough decision and if there is not any further community spread it always looks like this was out of proportion, but I must say you can't prove prevention," she said.
"So I think this is something that the Victorian government needs to be thinking about very hard today in terms of whether the best thing for us is to go into lockdown so we don't have a third wave in Victoria.
"I think if there is a time to really get this under control the time probably is now."
But other experts are more confident in Victoria's contact tracing system.
Chair of the Coalition for Epidemic Preparedness Jane Halton told Today she was reassured by a high number of Melburnians coming forward for testing.
"I really hope we don't need to lockdown, but everybody right now needs to read that list of what the hotspots are, think about where they have been, get themselves tested, if they actually have any symptoms, so no a lockdown will not be necessary," she said.
The Premier is expected to speak before midday on Friday, with high-level briefings underway this morning.
One of the five cases announced on Thursday was believed to have had some contact with Camberwell Grammar School, Department of Health COVID-19 response commander Jeroen Weimar said. The school closed on Thursday.
Genomic sequencing has confirmed that at least six of the 13 cases are the more contagious UK variant B.1.1.7 strain of COVID-19.
On Friday morning, there were 29 different Tier 1 exposure sites - which require mandatory 14 days of isolation for attendees- in 14 different suburbs across Melbourne.
There are exposure sites in Brighton, Brandon Park, Clayton South, Glen Waverley, Heatherton, Keysborough, Maidstone, Melbourne airport, Melbourne CBD, Moorabbin Airport, Noble Park, Springvale, Sunbury, Sunshine, Taylors Lakes and West Melbourne. There are eight in Sunbury alone.
Professor Catherine Bennett, the inaugural chair in Epidemiology at Deakin University, said the detection of fragments in wastewater samples earlier this week would be at the forefront of the minds of government advisers this morning.
Yesterday the government confirmed at least one case had been linked to wastewater samples in the Coburg- Pascoe Vale-Reservoir catchment, but there were also traces of COVID-19 found in Roxburgh Park, Broadmeadows, Westmeadows and Glenroy that had not been accounted for yet.
"That's probably going to create a level of nervousness that there are missed cases and that's where it is so important that that you know people are really checking out those exposure sites, and getting tested if there were there, or if they got symptoms," she told 3AW.
The outbreak, which authorities believe may have begun with the use of a nebuliser inside the hotel, prompted several states to tighten their borders to travelers from Greater Melbourne yesterday.
South Australia snapped its border shut to travelers from Melbourne at midnight on Thursday, while Queensland will ban entry to visitors to the city's exposure sites from 1 am on Saturday. Western Australia also announced its hard border to Victoria would be extended for at least another seven days. NSW remains open to all Victorians, but incoming passengers are being screened.
NSW Premier Gladys Berejiklian reaffirmed on Friday morning she had no intention of closing the border with Victoria.
"We think shutting borders and locking down community should be the last option, not the first option," she told Seven's Sunrise program.
"We are hopeful that the Victorian government and the health experts will get on top of this as soon as possible and we don't feel at this stage there is any need to close the border.
"We have seen the devastation caused last time that happened and as far as NSW is concerned … the only time we closed the border to any state was when Victoria had in excess of 150 daily cases."