Health officials are now investigating the movements of a New Zealand traveller who tested positive for Covid-19 after she flew into Sydney last week.
The Ministry of Health today said it would continue to "fully investigate" the circumstances of the positive result, including the woman's travel history.
The woman is currently in a "health hotel" in Sydney undergoing quarantine after she arrived on an Air New Zealand flight to Australia on July 20.
The Ministry of Health said at this point it appeared the person might have been a previously unconfirmed case from March and this was likely to have led to the positive test result.
Auckland's Regional Public Health was now following up with household contacts and other close contacts.
The Ministry of Health had adopted a risk-based approach, and testing and self-isolation had been implemented for close contacts.
The woman, who does not want to be named, said there were about 30 people considered close contacts who had been tested. She said most had now returned negative results for Covid-19, although some were still waiting to hear back.
The woman told NZME from her hotel isolation room she was feeling "perfectly fine" despite testing positive.
"I'm just very healthy and very lucky to be honest. I think people need to be aware that there are different cases out there and you can be asymptomatic and still be positive."
She believed she had contracted the illness on a flight returning to New Zealand from the United Kingdom in March.
She lost her sense of smell and taste but was unable to be tested because under strict criteria those symptoms were not considered Covid-related in the early stages of the disease spreading across the globe.
She said, as with the flu, she would have been infectious for a period back in March but her positive result months later did not mean she was still contagious.
It wasn't until she arrived in Australia and tested on July 22 that she learned she was positive for Covid-19.
She was shifted to a different government-managed isolation facility after her results came in. She is now waiting to leave when her fortnight ends.
She was allowed outside every day for fresh air, wearing a face mask and gloves as safeguards.
The woman is the third person in recent weeks to test positive after travelling from New Zealand.
A second woman passed through Auckland on a flight from Los Angeles to Sydney on July 6 but she did not leave the airport.
Health officials said while there were not considered to be any closed contacts who needed to be traced or tested, Inquiries were continuing with the airline and airport.
Meanwhile, widespread community testing is underway this weekend in Queenstown, Christchurch and Auckland after a Kiwi traveller tested positive when he landed in South Korea on July 22.
The 22-year-old man visited a number of shopping centres in Auckland and tourist attractions and eateries during a short holiday in the South Island before leaving the country.