NSW residents have been told to be on "high alert" after three cases of COVID-19 were confirmed in Albury on the NSW-Victoria border and as the outbreak escalates in the southern state.
NSW Premier Gladys Berejiklian on Thursday said health authorities are working to flush out any potential "seeding" of the virus that's occurred in border communities.
"We need to make sure there hasn't been any seeding prior to that rate of community transmission becoming apparent in Melbourne," she told reporters in Sydney.
"We should all be in a state of high alert.
"What's occurred in Victoria is a wake-up call for all of us."
She did not announce any changes to restrictions in NSW but warned the widespread community transmission in Victoria is a huge risk for the state.
Ms Berejiklian said it would be up to a fortnight before the situation became clear, with health authorities aware the virus may be "bubbling away" under the surface.
"So far the signs are positive but we won't know for sure for a couple of weeks," she said.
The premier reiterated that all residents of NSW-Victoria border towns should stay put for the time being, and those from elsewhere in the state should not approach the border.
Ms Berejiklian this week said her government will also consider either establishing a border north of Albury or making exemption permits harder to get if there's an increase in cases.
NSW reported 13 new cases of COVID-19 on Thursday - 11 in hotel quarantine and two family members in Albury flagged earlier in the week.
An additional family member in Albury tested positive to COVID-19 after the 8pm deadline for case numbers, NSW chief health officer Dr Kerry Chant said on Thursday.
One of the three Albury people who came down with the virus had previously visited Melbourne, where dozens of new COVID-19 cases are being reported daily.
NSW residents returning from virus-hit Victoria are not yet required to spend 14 days in hotel quarantine, but have been told to self-isolate at home for that period.
Ms Berejiklian said that if the government enacted hotel quarantine for those returning from Victoria, NSW residents were unlikely to be charged. The NSW government would instead look to bill overseas returnees first.
More than 125,000 exemption permits were issued by Thursday for people living in NSW-Victoria border communities, allowing them to cross between the two.
NSW Police Commissioner Mick Fuller on Thursday said police would support the decision to enforce any border north of Albury if it became necessary.
"We would make that happen to protect the people of NSW," Mr Fuller told reporters.
"If the health orders are breached, if the virus does get into border towns, it will put enormous pressure on the government for tougher restrictions."
NSW has also tightened procedures at Sydney Airport after passengers were allowed to disembark a flight from Melbourne without a second health screening.
Dr Chant said all but five passengers on Jetstar flight JQ520 - who left the gate area before health staff had finished screening an earlier flight - had since been tested for COVID-19.
Jetstar on Thursday refused to take blame for the error, with chief executive Gareth Evans saying the risk to the NSW community was "very, very low" as passengers had already been screened in Melbourne with temperature and ID checks.
Australian Associated Press