New Zealand's top health boss has rejected suggestions the country is being too soft on people who have tested positive for Covid, amid revelations a high school student now has the virus.

Cabinet Ministers will meet tomorrow to decide whether Auckland might be eased into alert level 2, stay at level 3, or moved to full lockdown.

Director-General of Health Ashley Bloomfield confirmed today a Mt Albert Grammar student in Auckland had tested positive - a person who was a close contact of the family whose members have tested positive.

He did not know if the student was one of the four probable cases announced yesterday.

He said some of the original family who had tested positive were in a quarantine facility but not all of them.

"I don't think we have been soft on this at all. We don't round up people in New Zealand, Mike," Bloomfield told Newstalk ZB's Mike Hosking this morning. "We round up sheep, we don't round up people."

Tomorrow's Cabinet decision on the future of the lockdown will depend on factors including the extent of the new Covid-19 outbreak, the containment of known chains of transmission, and whether the source of infection has been found.

Bloomfield would not say how he thought the decision would go. "We are getting all our information together so we can get the best possible advice. I feel confident we will have a lot more good information to inform a good decision."

Bloomfield told Hosking: "We get closer every hour" to finding patient zero, and the source of the latest outbreak.

He said it was only a "low possibility" the virus came in on freight - one of the family members works in a coolstore that takes imported frozen goods from overseas.

"We are working flat out to do the contact-tracing we need to do and trace back to find out what the source of this infection is," he said.

But Kiwis would have to wait until 1pm for the latest information on testing results and a full update.

He rejected a suggestion he was playing down the cases and the possibility of community transmission. "I don't think advising on getting Auckland into alert level 3 within about six hours is playing this thing down."

Kiwi epidemiologist at Melbourne University, Tony Blakely, said the Government response had been impressive, but he told Hosking it was "bizarre" how the virus had arisen again. He did not believe it could have come in on freight.

Prime Minister Jacinda Ardern and Bloomfield will today reveal the first trends from the push for mass testing, following the re-emergence of community transmission on Tuesday.

Auckland moved to alert level 3 at midday yesterday, inundating testing stations and supermarkets while others clogged up police checkpoints as they tried to flee the city before lockdown lite started.

There are now 26 active cases (confirmed and probable) of Covid-19, after a woman in managed isolation who arrived from Pakistan on August 7 tested positive yesterday.

The four cases of community transmission in a South Auckland family were isolating in their home. Four probable cases - two work colleagues and two relatives - have been linked to them, while 208 close and casual contacts have also been contacted.

They are among up to 1000 people who must stay at home until contacted by health officials, according to a new Public Health order from Bloomfield.

The order also applies to employees or contractors at two workplaces connected to the family, visitors to those workplaces and anyone who lives with those people. They can be forced into quarantine, if necessary.

The Government also moved to enhance contact-tracing by passing a Public Health Response Order requiring businesses nationwide to display QR codes at all entrances. Businesses have a week to comply.

A silver lining is that more than 100,000 people have downloaded the Covid Tracer app since the community transmission cases were announced.

Bloomfield continued to push for more people to download and use it, and if they couldn't, then to keep a diary of movements and contacts.

Testing stations in Auckland were deluged yesterday, and people were asked for patience as they waited for hours to be serviced.

Others tried to flee the city before noon, with traffic backed up on the outskirts of Auckland at police checkpoints.

A delay in setting up the Bombay Hills checkpoint even allowed one man to escape Auckland and drive to his parents' place in central North Island an hour after alert level 3 was meant to be in place.

Ardern's plea not to panic-buy fell on deaf ears, pushing Countdown to introduce new opening hours - 8am to 9pm - and put limits on buying certain products including flour, toilet paper, hand sanitiser and paracetamol.

Meanwhile Ardern traded verbal blows with National leader Judith Collins and deputy leader Gerry Brownlee, with the Prime Minister accused of lacking transparency and sitting on information.