The ACT has recorded three new cases of coronavirus, as plans to ease further restrictions on Friday are put on hold.
It's the first time in more than a month anyone in the territory has tested positive for the virus.
The three cases - one woman and two men all in their 20s - were detected in the same household and were linked to the Melbourne outbreak
Two arrived in the ACT from a Melbourne hotspot on Thursday before mandatory quarantine was implemented and the third person is a household contact.
A small number of close contacts have been identified.
Prior to being tested, the trio had visited the Fyshwick Markets on Saturday, July 4, between 3pm and 4pm and Westfield Belconnen on Monday, July 6, between 12pm and 12.30pm.
ACT chief health officer Dr Kerryn Coleman said the risk to the broader community was low, however anyone who attended these locations during these times should be vigilant and monitor themselves for symptoms.
The ACT had not recorded a new case of COVID-19 in more than one month. The total number of cases in the territory is now 111.
Dr Coleman urged anyone who had returned from Melbourne before mandatory self-isolation was put in place to be vigilant of their health and get tested if they showed any COVID-19 symptoms.
Chief Minister Andrew Barr said it was likely the ACT would not move ahead with further easing of restrictions due for Friday.
"The community should expect the implementation of stage three is likely to be postponed until we have a better understanding of the Victorian outbreak and the impact on the ACT," he said.
"We cannot put the hard work of this community at risk by moving too far, too fast."
Anyone who arrived in the ACT from Melbourne since Tuesday has been required to self-isolate for 14 days.
The new cases arrived in the ACT before this direction was in place.
Dr Coleman said anyone who had been in Melbourne recently and had not been ordered to quarantine should be extremely vigilant for symptoms and get tested if any appeared.
NSW Premier Gladys Berejiklian on Wednesday said she would consider forcing people returning from Melbourne to quarantine in a hotel at their own expense.
But Dr Coleman said she was happy with home quarantine and people's compliance.
"It's actually much easier for people to stay in quarantine while they're at home rather than a hotel," she said.
On Friday, the ACT was due to move to stage three of restriction easing which would allow gaming and gambling venues, strip clubs and brothels to reopen and outdoor gatherings of up to 250 people.
Dr Coleman said she would assess the situation in the ACT and advise the government tomorrow on easing restrictions.
"In the next 24 hours I will be seriously looking at what this means for the ACT as well as how many travellers have come in and what the implications are," she said.
"At this point in time I'm not considering going backwards, I think the most that would be requested is a pause."
Anyone who wants to return to the ACT from Victoria now has to gain an exemption to do so, after the NSW-Victorian border closed at 12.01am Wednesday.
So far, the ACT government has received about 200 exemption applications. This includes both people returning home to the ACT and those from Victoria wanting to enter the territory.
Dr Coleman said anyone in quarantine should expect to have spot checks conducted on them multiple times over the 14 day period to ensure they are complying.
She said the situation would need to be monitored closely over the next two weeks to determine if there was community transmission in the ACT as a result of the Melbourne outbreak.
"When I got the telephone call this morning must admit my heart skipped a little beat," Dr Coleman said.
"At this point in time it's very difficult to tell [whether we have community transmission].
"It is now partly the community's job to say, let's get tested, let's stay vigilant and see if there is community transmissions."
It comes as Melbourne continues to grapple with escalating case numbers and just hours after the NSW and Victorian border was closed.
NSW on Wednesday recorded eight new COVID-19 cases including seven in hotel quarantine and a woman in her 30s from southwest Sydney.
A Victorian teenager holidaying in Merimbula on the NSW south coast has also tested positive.
Melbourne entered its second lockdown on Wednesday with people only allowed to leave the house for work, exercise, care or essential shopping.
The state recorded another 134 cases overnight, after revealing yesterday the biggest daily increase since the pandemic began with 191 new cases.