There were just three new cases found in NSW in the 24 hours, all of them in Western Sydney, which were detected amid more than 32,000 tests.
NSW Premier Gladys Berejiklian thanked everyone for having a quiet New Year, and said the pandemic continued to be "an evolving situation" where restrictions could continue to change.
None of the three new cases are linked to the Avalon cluster, and none were in Wollongong.
There were two overseas cases found in hotel quarantine.
NSW Chief Health Officer Dr Kerry Chant revealed that health investigations had revealed that both the Croydon cluster and Wollongong's two cases had now been linked to the Avalon cluster from a genetic perspective.
However, they are still searching for how transmission to Wollongong and Croydon occurred, with Dr Chant saying Wollongong's Swallowed Anchor bar and restaurant may provide a "missing link".
She said a case from the Croydon cluster and a case from the Wollongong cluster both attended the Crown Street venue on December 19.
Late on Thursday night, NSW Health issued an alert for the bar and restaurant, saying anyone who attended there at any time of the day on December 19 must get tested immediately and self-isolate until they receive further advice from NSW Health.
"There may have been a transmission event at that venue," she said.
"What we're looking at is whether they were both infected at that time and date. For the abundance of caution, everyone at that venue on the 19th needs to get tested and isolate.
"There may have been a person in that cluster who may have had COVID at that time, who had a link to the northern beaches.
"Other people may have unknowingly been infected."
She said it may turn out that the restaurant was not the missing link, but said it would be an "amazing coincidence" if it was not linked in some way.
Dr Chant again thanked Wollongong residents for turning out in high numbers to be tested, but noted the numbers had dropped off in the city on New Years Eve.
She noted Wollongong had had COVID-19 cases before and had always been "amazing" when it came to testing responses, so she was confident that health authorities would be able to work with the community.
"My call out to the Wollongong comm is that you have been amazing over recent says, but this has to be a sustained effort," she said.
"Please continue to come out for testing in the coming weeks so we can be assured we are not missing any chains of transmission in that area."
She also said sewage testing had now become positive in Wollongong .
The state's ongoing sewage surveillance program has detected fragments of the virus that causes COVID19 at a sewage treatment plant in Wollongong.