The ACT has recorded 19 new locally acquired cases of COVID-19, taking the total number of active cases in Canberra to 28.
One of today's new cases was a student at Lyneham High School, who attended classes over four days while infectious.
Another of the cases is a worker at an aged care facility in Tuggeranong, who had received one dose of a vaccine and unwittingly worked three shifts while infectious.
Of the 28 cases so far recorded, ACT Health said 12 were still under investigation to identify the source of the infection.
The ACT government has also extended the territory's lockdown — initially set to end this Thursday — for another two weeks, until at least September 2.
Aged care worker infectious at work
Chief Health Officer Kerryn Coleman confirmed one of today's new cases was an aged care worker at Greenway Views Village in Canberra's south.
It is the first time COVID-19 has been detected in an aged care home in Canberra since the pandemic began.
"Investigations indicate that the staff member unknowingly worked three shifts at the village during their infectious period from Tuesday, August 10 through to Thursday, August 12," Dr Coleman said.
The worker became symptomatic on Friday and underwent a COVID-19 test.
"We are putting in additional measures; we have a team there now and we are including looking at full PPE for staff.
"We are communicating with the family and guardians of residents and staff to answer questions and keep them well informed."
Dr Coleman said all residents and staff would be tested for COVID-19 today.
Canberra's lockdown extended
Chief Minister Andrew Barr said in light of today's surge in cases, the ACT's lockdown would be extended for at least another two weeks.
"The numbers indicate the virus is active in the community," Mr Barr said.
"Lockdowns are a proven measure to suppress chains of transmission of the virus."
The lockdown will now last until at least September 2.
"We will assess the situation each and every day and if we can end the lockdown earlier we will," Mr Barr said.
"We are finalising details of this extension and will supply a comprehensive set of information for the community and businesses at tomorrow's press conference."
The announcement came as the Northern Territory government revealed a man who transited through Canberra Airport on August 12 had tested positive to COVID-19 in Darwin, sparking a three-day lockdown.
It is not yet known whether Canberra Airport will be identified as an exposure site later today.
Rise in cases not 'particularly alarming' to health authorities
Dr Coleman said today's rise in numbers was "not unexpected".
"We are continuing to work with over 6,500 people who have self-identified as close contacts. This number continues to grow and will continue to do so," she said.
"We are expecting to see cases rise, this growth in cases is what we see when we talk about cases coming into a community where there is very little restriction on its spread.
"So, we will see a rise in cases and then, as the impact of the lockdown does start to work progressively moving forward, those cases will fall."
There were more than 5,000 COVID-19 tests conducted in the ACT in the past 24 hours.
