Eleven new cases have been recorded in the 24 hours to midnight on Monday, including two linked to the Arcare Maidstone aged care facility reported on Sunday.

All cases have been linked to existing outbreaks, the Health Department confirmed via Twitter.

The department said eight cases are primary close contacts of people who have already tested positive for COVID-19 and have been quarantining during their infectious period.

It remains unclear if the cases are linked to the city’s outbreak of the Kappa variant, which began in Whittlesea and has spread to several locations across Melbourne, or if they are linked to the more infectious Delta outbreak.

There are 10 known cases in the Delta outbreak, with the source of infection for the first cases still unknown.

Infectious diseases expert Sharon Lewin suspects the variant could have leaked from a hotel quarantine or from a returned traveller who was provided with an exemption to isolate at home.

“There are exemptions for diplomats and other people … but those are actually really quite rare,” she told 3AW radio.

“That is another source that the authorities are going to be investigating.”

Professor Lewin and her team are continuing to comb through genomic sequencing data from across the country for answers.

It is unclear if the new cases will dent Melbourne’s hope of emerging from lockdown on Friday but Professor Lewin remains optimistic.

“It really depends on the data that we’re going to hear about today about the origin of these nine cases. But so far so good,” she said.

Victoria’s Deputy Chief Health Officer Allen Cheng on Sunday said he expected restrictions would be eased as planned.

“Given five per cent of Victorians have been tested in the last seven days, if there was a big outbreak going on I would expect to have picked it up,” he said.

“That risk does fall over time but we are still concerned about that and that is where all our efforts are going.”

Professor Cheng said there was no “magic number” of people getting the jab to avoid future lockdowns, with only two to three per cent of Victorians fully vaccinated.

“Once you get up to much higher coverage rates, then it makes a whole lot of things easier,” he said.

“We may not need the intensity of restrictions. We may be able to only do contact tracing without having to do other things quite to the same level, and that is the benefit of vaccination.”

Federal Health Minister Greg Hunt on Sunday announced an additional 100,000 vaccines are being made available for Victoria.

The federal government has also extended its suspension of JobSeeker mutual obligation requirements until June 15.

More than 1900 primary close contacts of the original Kappa variant-related Whittlesea outbreak were released from isolation on Sunday.

Six train services from Merlynston Station to Flinders Street Station were added to the list of over 350 exposure sites late on Sunday evening.

Some 24,265 Victorians were tested on Sunday and 17,719 received a vaccine dose at state-run sites.