Minister of Covid-19 Response Chris Hipkins says he is hopeful a lockdown can be avoided after a community case of Covid-19 surfaced in Auckland yesterday.
He told Morning Report preliminary results from genome sequencing suggest the woman's case is linked to a recent Defence Force cluster.
"That's looking pretty encouraging. We won't get the final result of that until later on this morning but it is looking more likely that we will be able to identify a link with the defence group that we're also dealing with, that will be very very helpful if we can do that."
The minister said there were a few more pieces to the puzzle to come, but that enough information would be available to make a decision this afternoon on whether to change Covid-19 response levels.
The woman in her 20s, who had no connection with the border or managed isolation, lives at the central city Vincent Residences apartment complex.
The minister said investigations, involving CCTV footage analysis, would determine whether the virus was spread from a nearby quarantine isolation facility.
RNZ reported that residences hadn't been told of the outbreak when its reporters arrived at the scene yesterday, with one man saying he had been rejected from getting tested at two centres because they were too busy.
Other residents, he said, had avoided self-isolating at the building when they were told by leaving immediately.
Hipkins said a testing team was dispatched to the building, but that the process took time and that health officials didn't have an unlimited number of staff available.
"My understanding is Auckland regional public health officials were liaising with the building manager. They did send people to the building, but it may have taken them some time to get there.
"I was assured last night that the testing team arrived on site, so we'll get an update on that later on this morning."
The woman who has the virus works at the A-Z Collection clothing store on High Street. She developed symptoms on Monday, went for a test on Tuesday and was told to isolate. Health officials say she called in sick on Wednesday, but after talking to her boss put on a mask and went in.
Hipkins wouldn't be drawn on whether the case should be investigated by WorkSafe, but said it was a disappointing situation.
"My message to all employers, up and down the country, is that if someone rings in sick and says 'I need to stay home', well, do everything you can to support them to do that. When it's related to Covid-19 there is additional financial support available to businesses if they need that."
His comments were echoed by Auckland Mayor Phil Goff. He told Morning Report incidents where people go into work when sick cannot be allowed to happen again.
"One thing that stands out in this case - the most basic rule that we all have to follow is, if you're sick with symptoms please stay at home.
"Particularly if you get tested and are advised to stay at home, you have to follow that advice. It's unbelievable that a person arrives at work after they've been tested before they have the results.
"Obviously if her story is true, any suggestion that pressure was put on employees showing symptoms to come to work, that's just crazy. That can't be allowed to happen."
He also urged all Aucklanders to take a precautionary approach and use face masks and the QR code.
"The advice that we get from the Ministry of Health this afternoon is going to be critical. Auckland Council is taking a precautionary approach ... we've closed the library, we've closed the art gallery, Auckland University is closed and people are doing exams online."
Officials are tracing the woman's movements over the weekend.
On Saturday, she went to Smith & Caughey's on Queen Street and Red Pig Restaurant on Kitchener Street. On Sunday and Monday she bought takeaways from Starbucks Queen Street, Sunnytown Restaurant on Lorne Street, and the Gateau House on Queen Street.
About 100,000 Aucklanders who work in the CBD are urged to work from home today.