Victoria has recorded four new Covid-19 cases in the community overnight, bringing the total number of infections in the state's cluster to 30.
The state also recorded two overseas acquired cases, which are currently in hotel quarantine.
More than 47,000 test results have been received in the past 24 hours.
Contact tracers have now identified more than 15,000 primary and secondary contacts who may have been exposed to the virus, with each of those people now in isolation.
Of those contacts, 1452 have been identified as primary close contacts associated with the Whittlesea and Port Melbourne cluster.
Yesterday, chief health officer Professor Brett Sutton warned "any one of (these contacts) could become cases over the next 14 days".
Speaking during Friday's press conference, Professor Sutton said the man known as case 5, believed to be the first case in the Whittlesea cluster, may have been out in the community for up to 12 days while infectious.
This is a major concern considering how quickly this virus has spread across Victoria in just a few days.
Friday's case numbers are significantly lower than the 11 new infections announced on Thursday, and would come as welcome news to the thousands of Victorians heading into their first day of lockdown.
However, Professor Sutton warned Victoria is not out of the danger zone yet.
"It is not over yet. We can get 10 tomorrow, 20 tomorrow we absolutely have to recognise that there are thousands and thousands of close contacts still to go through the incubation period, who could become symptomatic," he said.
Under the seven-day "circuit breaker" lockdown, residents are only allowed to leave their homes for five reasons, including getting food and supplies, authorised work, care and caregiving, exercise for up to two hours each day with one other person, and getting vaccinated.
A raft of restrictions around masks, gatherings, venues and businesses were also introduced and will be in force until 11.59pm on June 3.
Infectious disease expert Dr Michelle Ananda-Rajah warned the state could experience a "third wave" of Covid-19 infections if the situation isn't brought under control quickly.
"We have been here before. I think the stakes are higher this time because we have all the factors for what is essentially a perfect storm," Dr Ananda-Rajah told ABC's News Breakfast on Friday.
"We have a largely unvaccinated population, we have winter approaching and we have an unforgiving variant on the loose at the moment.
"Victoria is primed at the moment for a third wave and we need to do everything possible to prevent that from happening."
Why this cluster is different from previous outbreaks
The announcement follows fears Victoria's cases would explode overnight, after officials cites concerns about the number of exposure sites and the rapid rate of infection.
There are now more than 150 exposure sites spread across Victoria, with many of the venues bars, pubs, clubs and gyms where people are indoors and either dancing, singing or otherwise exerting themselves within close proximity to others.
The spread in workplaces is also a concern, with one of the recent cases in Port Melbourne spreading the virus to at least five colleagues, before also attending a number of high-risk venues while infectious.
"That young man who had been to loads and loads of busy, indoor settings – clubs and pubs and restaurants – they are high at risk," Professor Sutton said.
"Indoors, without a mask and exerting yourself – shutting, singing – these are high-risk activities and we need to watch them closely."
All of the cases in this cluster have been identified as the B.1.617 variant, commonly known as the Indian strain of the virus.
This strain is considered "highly-infectious" and has been officially listed as a "variant of concern" by the World Health Organisation (WHO).
On Thursday, Acting Premier James Merlino said that state has never experienced an outbreak of a strain that spreads this easily, saying the time between catching the virus and passing it on "is tighter than ever".
"Our contact tracers are identifying and locking down the first ring, second ring, and third ring within 24 hours. They have never done that before," he said.
"That's the fastest our contact tracers have ever moved within a 24-hour period, identifying and locking down first, second, and third rings of cases. But despite working as fast as this, and my thanks to all of our contact tracers, this variant is moving faster still."
The number of primary and close contacts identified by contact tracers has surged past 10,000, with chief health officer Professor Brett Sutton warning "any one of them could become cases over the next 14 days".
"There's been opportunities to spread to people. The other clear element is the infectiousness of the virus. When we see a member become infected, almost all the household is infected," he said.
"It speaks to the infectiousness of this B.1.617 variant, but also the cycles it's going through. It really is rapid and that's led to the exponential increase."
Another factor causing particular concern is the growing list of exposure sites and the kind of venues and businesses that are being identified.