The new case is a close contact of a previously reported case.

There are now more than 4500 close contacts that have been identified by health officials from 39 exposure sites, up from the 3900 reported on Friday.

Of those, 3126 tests were from ACT testing sites and more than 1500 were conducted at private testing clinics.

Out of the more than 4500 tests on Friday, health authorities said 1983 negative tests have been returned so far.

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ACT Chief Health Officer Kerryn Coleman said genomic sequencing has confirmed a link with several cases in Greater Sydney, which has been experiencing a widespread Covid outbreak.

Dr Coleman said investigations are still ongoing as to how a 14-year-old student at Gold Creek School became infected with the virus, due to them not being linked with other cases in the ACT.

Testing clinics across the ACT have been experiencing significant surges in demand following the lockdown announcement, some having to wait more than eight hours, while others were told to go home and come back the next day.

Chief Minister Andrew Barr said a record number of tests had been carried out in the past day, when there were more than 4500 conducted. He said that was more than 1 per cent of the population of Canberra, and a good sample to track the virus.

A test was conducted every 45 seconds at EPIC.

Testing capacity is expected to increase as the lockdown continues, now in its second day.

However, Health Minister Rachel Stephen-Smith said cars still had to be turned away despite waiting for several hours to be tested.

New traffic arrangements have been brought in at testing clinics to ensure the flow of cars.

The government is looking to restart operations at the Kambah testing clinic, which had been closed for several months, in order to allow more testing.

Mr Barr said while news of one new case was a good outcome, given the outbreak in Sydney, he said the lockdown was one day at a time.

"[Sydney] serves as a reminder as how it can get away from us quickly," Mr Barr said.

"I'm pleased we locked down when we did and it was the right decision, and it clearly reduced the risk to our community.

"If this continues, where we have high levels of testing and continue to get low case numbers, and isolate close contacts, that is the best public health response we can put in place.

"Throughout the pandemic we have been cautious and listened to the advice of the chief health officer. Clearly the lower case numbers and the closest we are to zero, the closer we are to coming out [of lockdown]."

Additional staff from the ACT public service and staff from ACT Health have been drawn upon by the government to boost capacity, as well as those from the private sector.

ACT police said no fines have been handed out during the lockdown and there was good compliance levels with the lockdown restrictions in the community.

In the past 24 hours, there were 2254 vaccines administered, bringing the territory's total to 167,332 vaccine doses.

Meanwhile, investigations continue into how the virus came into the ACT.

ACT Health officials have not ruled out the possibility that the Covid-positive case in Gungahlin, which sparked the lockdown, was not patient zero.

Mr Barr said a decision on whether the seven-day lockdown will be extended or not will be made in coming days.

"It won't be made tomorrow, likely it will be closer to the end of the seven-day period but won't be on the last day, so that gives a span of a few days," he said.

"But [the decision] has to be based on the current information and that's what we're getting through with the high levels of testing and the entire public health response."

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