NSW has recorded five new local COVID-19 cases, including a man in his 40s who sought medical treatment at a western Sydney hospital emergency department and was diagnosed with the virus.
Victoria, meanwhile, has agreed to reopen its border to those in regional NSW - but will remain shut to those in greater Sydney.
Three locally-acquired cases were recorded in NSW in the 24 hours to 8pm on Sunday, all connected to the 26-person Berala cluster.
Another two were confirmed after the 8pm cut-off - a man in his 40s who presented at Mount Druitt Hospital on Saturday with respiratory illness, along with one of his household contacts.
The man was confirmed COVID-positive and transferred to Westmead Hospital for treatment, while Mount Druitt Hospital emergency department has been deep cleaned and reopened on Monday.
"Investigations are under way to assess potential close contacts, including staff and patients," Western Sydney Local Health District said in a statement.
Another eight COVID-19 cases were uncovered in travellers in hotel quarantine.
Chief health officer Dr Kerry Chant on Monday told reporters the risk profile for other people in the emergency department at that time is still undetermined. The source of the man's infection is not yet known.
The potential Mount Druitt exposure incident comes as NSW continues to "mop up" two Greater Sydney outbreaks.
The 24-hour tally of three positive people came from more than 18,000 tests, prompting fresh calls from authorities for an uptick in testing.
"NSW under the circumstances is doing relatively well but we are in the phase of mopping up, we are in the phase of really trying to identify any community transmission," Premier Gladys Berejiklian said.
"(We want) to make sure any chains which exist in the community which we hadn't picked up before have been and are being picked up."
Victorian authorities on Monday elected to lift travel restrictions for those in regional NSW from 6pm, including for Victorians still attempting to travel home after the NSW-Victoria border was quickly closed in early January.
Victoria remains off-limits to those in greater Sydney - which includes the Blue Mountains and Wollongong but not the Central Coast.
"The trend is positive but there are ongoing cases, ongoing new exposure sites, ongoing transmission for the Greater Sydney area," Victorian chief health officer Dr Brett Sutton told reporters on Monday.
Several new NSW venues, including the Costco in Casula, Myer in Bankstown and Coles in Ashfield, have also been declared potential exposure sites.
Late on Sunday, NSW Health issued an alert for Bankstown Central Shopping Centre over two separate days, as well as casual-contact alerts for a Service NSW site in Bankstown and a Thai supermarket at Marrickville.
Other casual-contact alerts were issued on Monday for Campsie Super Fresh on January 2 and Campsie Hills Seafood Shop on January 8, as well as the Australia Post at Hurlstone Park on January 5.
Meanwhile, residents from the northern part of Sydney's northern beaches celebrated "Freedom Day" on Sunday, having been let out of lockdown.
But Ms Berejiklian warned NSW residents hotel quarantine leaks and local virus outbreaks would likely continue to occur around the state, regardless of the stringency of quarantine regulations.
She also said regulations had changed from Monday to enforce mask usage at all times for hotel quarantine workers.
"We have to be very honest - there is no way of eliminating this virus so long as it exists around the world," Ms Berejiklian said.
"Perfection is not possible during a pandemic. As much as we'd like to think there is perfection, there's not. We have to assume there will be incidents where there's concern but let's put things into perspective."