Victoria has reported a further six locally acquired coronavirus cases on Monday in addition to the five announced earlier today.
Acting Premier James Merlino told reporters the outbreak may get worse, and said the situation was "incredibly serious".
"The next few days remain critical. I want to be very clear with everyone, this outbreak may well get worse before it gets better," he said.
Of the five cases reported on Monday morning, two were related to the Whittlesea outbreak, one is a contact of a previous case linked to the Star Car Wash and another remains under investigation as the source is unknown.
Mr Merlino did not specify the details around the fifth case.
He said the state was managing 4200 primary close contacts across all of the exposure sites.
Concern over emerging outbreak
Health Minister Martin Foley told reporters of the latest six cases three related to emerging outbreaks in private residential aged care.
One is the son of the initial mystery case in the Arcare Maidstone aged care facility reported on Sunday.
Mr Foley said he did not work at the facility but was still linked to that outbreak.
The second is another staff member at Arcare Maidstone, who worked alongside the initial case.
She was not vaccinated and also worked at the BlueCross Western Gardens aged care facility in Sunshine.
The third is a woman aged in her 90s who is a resident at Arcare Maidstone.
Mr Foley said she was asymptomatic and had been transferred to a separate hospital.
"The fact this outbreak has crept into a number of private residential aged care facilities is obviously a very great concern to the Victorian government," he said.
Chief Health Officer Brett Sutton said the new cases were emerging in "concerning settings".
"It has been a rapidly moving virus and the transmission that has occurred in those high-risk [aged care] settings has been very substantial," he said.
"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."
Professor Sutton could not say whether or not the state's seven-day lockdown would be lifted on Thursday.
"We have to prepare for anything. We don't know what will unfold over coming days," he said.
Victoria's COVID-19 testing commander Jeroen Weimar added three schools in Melbourne had been closed as the latest cases emerged.
Mr Weimer said they were closed out of caution, with one school linked to three possible cases.
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