Authorities in Victoria, Australia, reported the highest increase in new locally acquired COVID-19 cases in over a week on Monday, as they try to track down the source of the highly virulent Delta variant detected among illnesses.

As residents of the state capital Melbourne await word on whether a lengthy snap lockdown would end as planned on Thursday night, authorities recorded 11 new cases, up from only two the day before. All of the new cases, however, were linked to previous clusters.

When asked if some portions of the city could remain closed while others eased limitations, Victoria state Chief Health Officer Brett Sutton told reporters in Melbourne, “Nothing is on or off the table.”

On Monday, Melbourne entered its 11th day of severe lockdown after officials discovered the Delta virus type for the first time among illnesses on Friday, which they claimed was likely to spread more easily than many previous strains.

The source of the Delta variant infections has yet to be determined, and no genetic matches with other cases in Australia have been found thus far.

With the addition of these three cases, the total number of locally acquired cases in the latest outbreak in Victoria, Australia’s second-most populous state, now stands at 83.

Two cases disclosed on Sunday were recorded after the midnight cut-off period, resulting in Monday’s figures.

Officials said all of Monday’s locally acquired cases are linked to previous clusters, with eight of them being close contacts who isolated themselves while contagious.

The Delta variation, which has been categorized as one of the four COVID-19 variants of concern by the World Health Organization due to indications that it spreads more easily, is most likely to blame for the most recent disastrous outbreak in India.

With snap lockdowns, regional border restrictions, and tight social distancing measures, Australia has largely contained previous outbreaks, with COVID-19 cases and deaths totaling slightly over 30,150 cases and 910 deaths.

Around 20% of Australia’s adult population has gotten a first dose of the vaccine, with over 5 million doses provided thus far.

Last year, Victoria was put on lockdown for nearly three months to contain a second wave of COVID-19, which killed over 800 individuals and accounted for approximately 90 percent of all coronavirus deaths in Australia since the epidemic began.