NSW has recorded eight new locally acquired virus cases, including three cases flagged on Wednesday that ended a 12-day streak without any community transmission.
NSW Chief Health Officer Kerry Chant said the eight new cases were from two separate clusters that were being investigated.
The five are linked to the 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 way we think it unfolded was that there was a healthcare worker, who did not have symptoms, who works at Liverpool Hospital," Dr Chant said.
The source of the second cluster - the three linked cases revealed on Wednesday - is still under investigation.
Another four cases were also diagnosed in hotel quarantine in the 24 hours to 8pm on Wednesday, bringing the state's total to 4072.
Multiple cases have also been diagnosed during the day on Thursday and will be included in Friday's numbers.
NSW Premier Gladys Berejiklian earlier on Thursday said it was likely more cases would come to light in the next few days.
"We anticipate that because we've identified these eight cases, that a number of close contacts and family members could be found to be positive as a result, so it's really, really important for everybody to stay on high alert," she said.
A spokesperson from Macquarie University confirmed that a student was among the recently diagnosed cases.
The university's Sports and Aquatic Centre and a Faculty of Arts building are closed on Thursday for deep cleaning, but are expected to reopen on Friday.
Anyone at the university pool between 5.30am and 10.30am on October 7 must be tested for the virus and isolate until they receive a negative result.
"Following guidance from the authorities, contact tracing measures are now underway and anyone who may have come into contact with the student will be informed to self-isolate and get tested," the spokesperson said.
Public health alerts have also been issued for Chemist Warehouse on the corner of Bridge and Rawson streets, Epping, and Surf Dive 'n Ski at Castle Towers Shopping Centre, Castle Hill.
While these new local cases have threatened the prospect of the Queensland border reopening on November 1, Ms Berejiklian accused her northern counterpart Annastacia Palaszczuk of "making up rules".
Queensland on Wednesday gave NSW 48 hours to find the source of three new cases before the countdown clock re-starts, as it insists the larger state must go 28 days without a single locally transmitted 'mystery' case.
"The Queensland government seems to be making up rules as they go along," Ms Berejiklian said.
"I don't know where they got that 48-hour deadline concept from and I certainly want to send a very strong message to our health experts in NSW - just continue to do your jobs well (and) ignore those artificial deadlines other governments are imposing on us."
Ms Berejiklian also flagged that the NSW government was considering making the Service NSW QR scanning code a compulsory feature for venues and businesses.
Meanwhile NSW Health issued an alert for anyone who attended the Ripples Restaurant in Milsons Point last Saturday, between 8pm and 10.30pm after one of the new cases dined there.
It said the restaurant failed to take the details of "a small number" of diners during that period, and that contact tracers were relying on public call outs to diners, all of whom are considered close contacts and must get tested and isolate immediately.
Ms Berejiklian said there was no excuse for businesses that did not strictly adhere to the COVID-safe rules.
"I have no patience anymore for people, and businesses in particular, that aren't doing the right thing.
"We've been extremely patient and tolerant to bring everybody on board but we can't have a few people let down the whole community."
There were 12,498 tests reported in the 24-hour reporting period, compared with 5970 in the previous 24 hours.