Authorities are working to determine how a Sydney firefighter was infected with COVID-19 as NSW records seven new locally-acquired COVID-19 cases.
Premier Gladys Berejiklian on Sunday said all seven cases were linked to the Northern Beaches, and six had been linked to the Avalon cluster which now involves about 122 cases.
The seventh new locally-acquired case - a firefighter from the Northern Beaches with links to the Belrose Hotel - is still under investigation.
Authorities have asked anyone who attended the Belrose Hotel - at any time in December - and developed symptoms to come forward for testing and isolate until a negative result is received.
"Generally, if you've been to the Belrose Hotel and have the most minimal of symptoms, please get a test," NSW Chief Health Officer Kerry Chant said on Sunday.
Dr Chant said a young employee of the hotel had recently been revealed through testing to have caught the virus two or three weeks ago.
However, the young man in his 20s was not working when the firefighter attended the hotel on 11 December, or when another positive case visited the hotel's bottle shop on 17 December.
"We're not looking at this gentleman in his 20s infecting this firefighter, what we're looking at is the missing link - who else was present at the Belrose," she said.
NSW authorities also flagged new possible infection sites at Casula in Sydney's south-west.
Dr Chant also urged NSW residents more broadly to get tested for any symptoms as the state reaches a "critical stage" of its coronavirus response.
"Unless we have those high testing rates, it does not give us adequate assurance that we are not missing undetected lines of transmission," Dr Chant said.
In the last 24 hours, have been added to the , including Zeus Street Greek in Drummoyne, Anytime Fitness Belrose and the B1-1 bus route covering Wynyard and Mona Value in both directions on 17 December.
Ms Berejiklian noted that a number of Sunday's new cases were detected on day 10 or 11 of the isolation period, showing how important it is that those required to isolate to do so for the full 14 days.
Sunday's COVID-19 update came as the Northern Beaches area barring indoor gatherings, following a three-day reprieve over Christmas.
Under the reinstated restrictions, outdoor gatherings of up to five people are permissible on the northern zone of the peninsular for either exercise or recreational activity, as well as similar gatherings of up to 10 on the southern zone.
Residents of each zone are only allowed to leave for essential reasons such as shopping for food or other goods and services, exercise, and getting medical care or supplies. Greater Sydney residents are banned from entering the region.
Ms Berejiklian said they hoped to have clear information on Monday or Tuesday on what New Year's Eve and the next few weeks will look like for everyone, including residents in the Northern Beaches.
"Every day that goes past gives us more information and more confidence to make decisions which we think will ease the pressure on communities at this stage," she said.
"And as we approach New Year's Eve can we please remind everybody that unfortunately singing, dancing, speaking loudly are all accelerants for transmitting the virus and therefore, those activities obviously are not allowed."
People in Australia must stay at least 1.5 metres away from others. Check your jurisdiction's restrictions on gathering limits.
If you are experiencing cold or flu symptoms, stay home and arrange a test by calling your doctor or contact the Coronavirus Health Information Hotline on 1800 020 080.