NSW recorded seven new locally acquired COVID-19 cases overnight, discovered as the result of a new record number of tests on Thursday.
NSW Premier Gladys Berejiklian said after almost 70,000 tests six of the new cases were people already in isolation while the other was someone who works on the Northern Beaches.
Ms Berejiklian thanked people in NSW for being so diligent with COVID-19 testing and social distancing.
"And I want to thank all our front line health workers and pathologists who have literally worked through the night to not only get those tests done but give people the results," she said.
"The system has really scaled up and I am incredibly proud of each and every person who is involved in doing those tests and the people who are coming forward and doing the right thing."
The new record of 69,809 tests comes a day after 60,000 tests were done on Wednesday which eclipsed the previous record of 42,000 in NSW.
Ms Berejiklian said people should continue to get tested on Christmas Day and Boxing Day, with more than 300 clinics open during the holidays.
She also encouraged people not to move around if they don't have to and to be careful of crowded places during the Boxing Day sales.
"We are still concerned about a potential spread through the Sydney CBD," she said.
"We want to make sure people who have gone back to their suburbs have not past it on to others."
Ms Berejiklian said it appears the latest outbreak has been constrained but we can't be too careful over Christmas and New Year.
"We do ask people to limit any activity in the Sydney CBD," she said.
"We know tomorrow is traditionally a day for Boxing Day sales but please we want to discourage people from going to the CBD tomorrow and please limit your activity.
"And if you are going shopping in the CBD make sure you wear a mask.
"We have already been in touch with retailers to make sure there is social distancing in queues and that there is a four square metre rule respected in the actual venues.
"All staff and people shopping should be wearing a mask inside those venues.
Ms Berejiklian said people shopping in their own local area should do the same.
NSW Chief Health Officer Dr Kerry Chant said four of the new cases were linked to the Avalon cluster and two were household contacts from previously un-linked cases in the Northern Beaches. One of those is still under investigation.
"After 69,809 tests in a 24 hour period I want to thank the community for listening to our message about coming forward for testing," she said.
Dr Chant encouraged people to please limit their social interactions during Christmas and respect the limits to household gatherings.
"This is a critical point in our response and if we work together we can decrease the chance of COVID spreading," she said.
"Most importantly don't risk passing on COVID to your friends and family. If you are in isolation you have to stay in isolation. Don't let visitors into your home and don't interact with any visitors.
"Even if you have the mildest symptoms please just don't go out and about."
Dr Chant said the best thing to do was to go and get a COVID test.
A full list of locations and public transport routes, and the associated public health advice, is available from the NSW Government website at https://www.nsw.gov.au/covid-19/latest-news-and-updates.