Ten more close-contact exposure sites were added to the list late on Tuesday night, with almost 2000 primary and secondary students at Harrison and their families to be sent into immediate quarantine.

St Thomas Aquinas Primary School in Charnwood and the Lake Ginninderra College canteen and gym were other education locations added to the growing list.

Canberra's Covid testing centres are already at capacity, with ACT Health forced to close the gates to EPIC on Tuesday because of high demand.

That demand is only set to increase, given the added close-contact exposure sites.

Harrison School has 1850 students enrolled in classes from preschool to year 10. All students who attended the school on August 11 and 12 will have to be tested and quarantine for 14 days. Their close contacts will also have to quarantine.

The Capital Chemist in Lyneham, Coles at Kaleen, GG's Flowers and Hampers in Farrer, IGA at Evatt and Yum Cha at the Belconnen Westfield food court are also close-contact locations.

Anyone who has been to a close-contact location during the exposure period must fill out a declaration form, immediately quarantine, get tested and remain in quarantine until advised otherwise.

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There are 45 active cases in Canberra after ACT Health confirmed 17 new positive cases on Tuesday.

ACT Labor senator Katy Gallagher on Tuesday night revealed her daughter Evie was one of the 17 new cases, and more cases will be announced on Wednesday at the government update.

Canberra's lockdown has been extended until at least September 2, with health officials racing to get on top of the Delta variant outbreak.

ACT Chief Minister Andrew Barr has told residents to leave home only for essential reasons, and the quarantine measures have put pressure on food delivery services.

The exposure-site list was expected to grow to more than 100 by Wednesday, with more than 7500 people already identified as close contacts of the active cases.

Lyneham High School and Gold Creek have already been caught up in the outbreak, which contributed to a record number of tests were conducted in the ACT on Monday, with 7350 samples collected.

Chief Health Officer Dr Kerryn Coleman said 10 of the new cases were linked to previous cases, and there were six sites across the ACT where transmission had been recorded.

Transmission sites have been identified at the Downer Community Centre, the Fiction nightclub, the Assembly Pub in Braddon, the Lennock Jaguar car dealership in Phillip, the Gold Creek School and Lyneham High School.

Dr Coleman said there were four cases linked to Lyneham High School, in addition to the primary case there.

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