The ACT government looked set to extend the lockdown for Canberra, ahead of a crucial cabinet meeting on Monday afternoon to consider the future of restrictions for the capital.
Canberra's lockdown is due to end on Thursday, but cases of the virus continue to be infectious in the community.
Only two of the 12 cases reported in the ACT on Monday were in quarantine for their full infectious period. Six were infectious in the community and the infectious status of four was under investigation.
Chief Minister Andrew Barr said he expected to make an announcement on any extension to the lockdown on Tuesday, following a cabinet briefing by the chief health officer.
Mr Barr said lockdown measures were effective in reducing spread and the territory would need ongoing public health measures in place beyond this week.
"We do not want all of the hard work over the last few weeks to go to waste by opening up too early," he said.
"Our lockdown measures are effective in reducing the spread of the virus but it is concerning that we are still getting cases infectious in the community."
Throughout the outbreak, Mr Barr has remained adamant a run of no cases in the community - and no mystery cases - would be essential to any easing of restrictions.
"The Delta strain is very, very challenging to contain," he said.
"We still have people who are infectious in the community, we still have cases that don't have a clear epidemiological link. This is concerning."
The sources of infection for 20 of the 261 cases in the territory are under investigation, including six cases reported on Monday.
Chief health officer Dr Kerryn Coleman said health authorities were still investigating whether the ACT had multiple introductions of the virus from NSW, but that didn't mean there was 20 different chains of transmission.
"Some of those  cases are truly just cases that have appeared that we're not sure of any links," Dr Coleman said.
"Some of those are well associated with these new clusters but we don't know what the source of introduction into those clusters were."
There are now 12 people in the ACT with Covid in hospital, three are intensive care and one is on a ventilator.
Eleven of those in hospital are unvaccinated, while the other had only one dose of the vaccine.
Twenty-five people have recovered from the virus.
There were 2262 tests carried out on Sunday. Mr Barr said this number needed to increase.
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Two new cases of Covid have also been associated with the Ainslie Village social housing complex. Dr Coleman said the cases were identified on Monday morning and would be included in Tuesday's case numbers.
The complex was listed as an exposure site on Sunday after a positive Covid case visited the location while infectious.
A response team was on site at the complex again on Monday.
"We've done extensive planning in these places, this is a concern but we have plans, we have lots of people on site, we have lots of engagement and we just continue to work with the communities and support them as much as we can," Dr Coleman said.
It is the second public housing complex to be caught up in the Canberra outbreak.
Condamine Court was listed as an exposure site last week. Tenants at the Turner complex expressed frustration at communication from the government and the ACT Council of Social Services said basic needs of tenants were being dismissed.
No further cases were associated with Condamine Court on Monday.
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