However, authorities were "very concerned" by the number of cases and exposure sites.
"I cannot rule out taking some further action," Merlino said. "We'll update people as soon as we know. It's fair to say the next 24 hours are going to be particularly crucial."
One of the infected people attended an Aussie Rules games at the MCG on Sunday night. Merlino stressed that AFL organisers had planned for such a situation.
Merlino thanked all Victorians for complying with new private and public gathering restrictions that took effect from 6pm local time yesterday.
New Zealand suspended quarantine-free travel with Victoria for 72 hours from last night in response to the outbreak.
Reported yesterday: 10 new local cases and no new cases acquired overseas. - 15,858 vaccine doses were administered - 26,180 test results were received
A man in his 60s, who was among the five cases announced yesterday, is believed to be the earliest known infection in the new outbreak.
The man, referred to as case 5, developed symptoms on May 17, with authorities believing he may have been infectious for almost 10 days before presenting for testing.
Later in the day it was announced four family contacts of the man also tested positive. He is also believed to have transmitted the virus to the first person discovered in the cluster, a man in his 30s.
That man then passed the virus on to three close family contacts spread across two households in Whittlesea, including a man in his 70s, a woman in her 70s and a preschool-aged child.
Everyone in the new cluster has been confirmed as having the Indian variant of the virus.
A raft of new restrictions were introduced across Melbourne from 6pm on Tuesday, including:
• A limit of five visitors per day for private households
• Masks required indoors for everyone aged 12 and over — even in workplaces — unless an exemption applies.
More exposure sites, including MCG
Multiple locations have been added to the list of sites visited by confirmed Covid-19 cases during their infectious periods.
A late night alert from Victorian health authorities sparked concerns thousands may have been exposed to the virus after a positive case attended the Collingwood/Port Adelaide game at the MCG on May 23.
The L word is getting closer. Would be somewhat cruel, but poetic if our 4th lockdown was announced on the 1st anniversary of the start of our 2nd wave. #COVID19Vic#Melbournehttps://t.co/OmQ6kwilme
