Workers in Auckland's CBD are being asked to stay at home on Friday if at all possible as health authorities race to find the source of a new community case of Covid-19.
A woman in her 20s returned a positive test on Thursday, but has no apparent connection with overseas travel, the border, or managed isolation.
Health authorities are racing to find her contacts and the source.
Auckland Mayor Phil Goff told Checkpoint it was not great news.
He had only just started seeing more people out on the streets enjoying the late spring.
Last Saturday, he said at an Italian festival in Newmarket there were people "really enjoying, having that freedom of getting together in a Covid-free world".
"And then we get another case of community transmission."
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He said the worst part about the case was the woman being told to isolate after taking a test, only to be told by her manager to return to work.
"That is frankly unbelievable. I just cannot understand that. It defies common sense.
"There's a lesson in that. You'd think that that was a lesson people didn't need to learn. If you have symptoms, get tested, while you're waiting for the test [result] stay at home, self-isolate - that's a basic rule."
Auckland Council will close its three offices in central Auckland tomorrow, along with a number of community facilities and venues, including: Auckland Central City Library, Tepid Baths, Auckland Town Hall, Waitematā Local Board office, service centres at Bledisloe House and Graham Street.
Goff said people needed to follow rules to keep the virus out.
"Really bad call by that manager to ask his staff member to come into work when she was sick and suffering from symptoms."
He said Covid-19 had a "crippling effect" on the finances of Auckland Council and the city's businesses.
Just when people were returning to the city and public transport use was back up by 70 percent, people were being urged to work from home again and wear masks when on public transport, he said.
"Please use your Covid Tracer [app]."
Goff said he got a call from Prime Minister Jacinda Ardern saying the government was not wanting to move the city to a higher alert level.
Auckland is in alert level 1.
"If they can trace where the virus has come from, that would be the first good news. They're doing the genome sequencing overnight, they'll have those tests tomorrow. If they don't know where it's come from, that puts us in a rather serious position."
He said if the source remained unknown, large scale events in the city might need to be scaled down.
"We've done it before, we'll do it again."
Prime Minister Jacinda Ardern has returned to Wellington from Auckland, following news of the community case, having visited an Auckland technology business that developed an artificial intelligence digital assistant.
She returned to the capital this afternoon and will inform New Zealand if alert level settings change.