There is growing expectation Victoria's seven-day lockdown will be extended beyond its Thursday deadline as the number of community-acquired COVID-19 cases continues to grow.

The state's latest lockdown is scheduled to end at 11.59pm on Thursday, June 3.

However, The Age reports senior government ministers met overnight for a high-level briefing from health authorities about extending stay-at-home orders.

A source close to the government, who spoke on the condition of anonymity, told the newspaper Victorian Chief Health Officer Brett Sutton's team was leaning strongly toward recommending a lockdown extension.

The state recorded three new locally-acquired cases on Tuesday, taking the outbreak total to 54.

There are now more than 300 COVID-19 exposure sites where Victorians could have come into contact with the virus.

Victoria health authorities have revealed concerning details about "stranger to stranger" transmission of the virus that contributed to the snap seven-day lockdown.

COVID-19 testing commander Jeroen Weimar singled out Melbourne shopping centres as venues of most concern where transmission may have occurred through "very fleeting contact".

"They don't know each other's names. That's very different to where we have been before," Mr Weimar said.

With this in mind, authorities are not ruling out an extension of the lockdown past the original seven days.

Health Minister Martin Foley would not confirm whether the state's current lockdown would be extended or if a ring of steel would be established between Melbourne and regional Victoria, but did not rule out the possibility.

"We do not know if there's going to be an extension or not," he said.

"As the Acting Premier pointed out yesterday, there is every prospect that things might get worse before they get better … and the aged care settings are quite troubling," he said.

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"Yes, we are making significant inroads to our contact tracing, through our support from millions of Victorians who are following the rules and doing the right thing, that is helping all of our processes, but we are not yet in a position to make that call.

"As soon as we do have those recommendations from our public health teams, we will make those announcements."

There are no longer any mystery cases in the state, with every case being linked to either the City of Whittlesea, Port Melbourne or Arcare Maidstone Aged Care.

All of the cases link back to the South Australia hotel quarantine breach.

Professor Sutton said on Monday that extending Victoria's current snap lockdown was a "day-by-day process".

"It has been a rapidly moving virus and the transmission that has occurred in those high-risk settings has been very substantial," Professor Sutton said.

"So we have to take it as a day-by-day prospect.

"With more numbers today coming through and those really concerning settings, especially in aged care, we are neck and neck with this virus and it is an absolute beast."

Under current lockdown conditions, Victorians cannot leave their home except for five reasons, including going to work, getting vaccinated or exercising.

All residents must stay within five kilometres of their home for shopping and exercise.

Face masks must be worn indoors and outdoors when leaving the house.

Victorians may also leave home to visit their intimate partner, their single social bubble buddy, or in an emergency – including those at risk of family violence.

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