New South Wales is investigating a mystery COVID-19 case after seven new community cases were recorded in the state on Christmas Day.
The mystery case is a previously recorded infection from 23 December which has not been linked to the current cluster.
Chief health officer Kerry Chant said it's likely the person, a hotel worker, was infectious two weeks ago.
"We know that this individual to date has not transmitted infections to others but what we are interested in is knowing how this person acquired the infection because the person is not linked to the cluster," she said on Friday.
Of the seven new cases six were already in household isolation. Premier Gladys Berejiklian said it is to be expected that more people sharing homes with confirmed cases will test positive in coming days and weeks.
"The direct contacts will start to test positive and that is where we will see a large number of case numbers eventuate."
More than 69,800 people were tested for the virus on Christmas Day and 300 testing clinics are open across the state to ensure those showing symptoms can be tested.
Berejiklian has urged Australians to be wary, and seek help if needed.
"Our health people and the supporting pathologists have just been amazing, so even if you get a symptom on Christmas Day or Boxing Day, please go and get tested, do not wait."
