A nurse at Sydney's St Vincent's Hospital has tested positive for coronavirus after working a shift while infectious.
NSW Health has issued a public alert, saying the casual nurse worked an evening shift on Wednesday.
"It is believed the nurse provided specialised care to a single patient, and had limited contact with a very small number of colleagues," NSW Health said in a statement on Friday night.
"Contact tracing is underway and the source of the infection is under investigation, though it is believed the source of infection occurred outside the hospital."
NSW Health said the case would be reported in tomorrow's numbers.
Earlier, 10 new cases were announced as being recorded in the 24 hours to 8pm on Thursday.
Five of the new cases were returned overseas travellers in hotel quarantine while the other five were locally acquired and linked to a known case or cluster.
NSW Health is warning that anyone who attended Westfield Parramatta on October 6 between noon and 12.15pm or October 7 between noon and 12.30pm and 4.30-5pm is considered a casual contact of an infectious person.
They should monitor for coronavirus symptoms and get tested if any develop.
The rise of new local cases has threatened the prospect of Queensland reopening its border with NSW on November 1.
Queensland had earlier given NSW 48 hours to find the source of three new cases before restarting the 28-day countdown clock that triggers border reopenings.
NSW Premier Gladys Berejiklian said it was effectively easier for Queensland to reach the 28-day goal as it had a smaller population than NSW, had a closed border, wasn't taking as many returned travellers in hotel quarantine, and was further away from Victoria.
"Zero community transmission is of course our aspiration," Ms Berejiklian told reporters earlier on Friday.
"All I'm saying to other states is look at what we're burdening in NSW, look at the GST contribution you get from us on average. Share the burden a little bit.
"I could easily say 'zero community cases' if I only had 700 quarantine people per week (but) we've got 3000."
The premier said she hoped to see open borders Australia-wide by Christmas, depending on Victoria's situation, and warned tourism could suffer if borders remained closed.
NSW Health said four of the new locally acquired cases reported on Friday are associated with a private health clinic cluster.
It said all indications were that one of the new cases is an old case most likely acquired when the virus was circulating at low levels in southwest Sydney in August.
Meanwhile, NSW Health is working with Potts Point restaurant Monopole to assess the risk to patrons and staff who may have been exposed to COVID-19 when a person who was infectious visited from 6pm to 8pm on October 4.
Contact tracing is under way and the department will contact close and casual contacts directly but urged anyone who was there to monitor for symptoms.
NSW recorded eight more locally-acquired cases on Thursday, including three flagged on Wednesday, ending a 12-day streak without any community transmission.
Five of the cases announced on Thursday were linked to a Liverpool Hospital dialysis cluster - one healthcare worker in her 30s, two women who visited her, and two household contacts aged in their 60s and 80s.
The source of the second cluster - the three cases revealed on Wednesday - is under investigation.
A spokesman from Macquarie University confirmed that a student was among the recently diagnosed cases, and contact tracing was under way.