Prime Minister Jacinda Ardern is working to establish what rules were broken after an Auckland prisoner caught Covid while he was transported to a North Waikato bail address, later infecting three members of his household.

Ardern said this morning that officials had confirmed how the man - a patched Black Power member - became infected after being freed on bail and immediatrly breaching those conditions by visiting four sites in Auckland,

"We now know how he got Covid ... when and who from," Ardern told TVNZ.

The man didn't necessarily catch Covid from the people who were driving him from prison to his bail address in Whakatîwai in north Waikato.

However the infection did occur after the man left Mt Eden Prison and before he arrived at his approved level 2 bail address.

The issue wasn't about the prisoner being remanded to a level 2 address, but how he got there, she said.

Ardern said the Government had now established and how and when he had got Covid and was now looking into exactly what rules had been broken because clearly some had.

When asked on Breakfast if it was a person in a vehicle that transported the person to Waikato, she said "no not necessarily". "Even in this circumstance it may not have been the people transporting them."

Ardern earlier confirmed one of the people transporting the 36-year-old prisoner was an essential health worker.

She also said the people would have dropped him off on the proviso that they then returned directly home and in this case this may not have been when the rules were broken.

"We are working on that, but the public health question is the one that takes priority."

Corrections has revealed the released prisoner made four stops including at two private addresses, before arriving at his bail address at Whakatīwai.

It appears to have been a breach of his bail conditions which required him to be collected by a family member and travel to the bail address without any unnecessary stops.

Immediately after release, the patched gang member breached his strict bail conditions despite a judge overruling a request to keep him in custody.

He stopped at two private addresses in Mt Albert and Māngere, a supermarket in Pokeno and on the side of the road, arriving at his bail address two hours and 19 minutes after leaving the prison.

The three new cases - including two Mangatangi School students - has the entire North Waikato rural community on edge as hundreds of people hurried to get tested yesterday in hopes of establishing how far Covid may have spread in the community.

Surrounding areas centred around Mangatangi in north Waikato are now in a bespoke level 4 until midnight Friday.

Meanwhile Aucklanders can finally smell the freedom in terms of takeaways and contactless shopping as the city emerges from its longest stint in level 4 tonight.

The move down comes as there are still numerous cases of Covid-19 emerging in the community each day with 22 reported yesterday.

Covid modeller Professor Michael Plank told TVNZ moving to level 3 was a calculated risk by the government and it was really important people didn't take it as a signal that virus has passed.

Plank said it was really hard to ring fence the virus and stop it jumping into a new household and spreading within that household. He believed the government could still eliminate the virus providing everyone did the right thing.

Senior Māori health researcher Dr Sue Crengle said there was a risk that with moving down level the virus would get away on New Zealand and it would find itself in a similar situation as New South Wales. "They had a long tail, they had less restrictions than we have and the virus got away on them."

Director-General of Health Dr Ashley Bloomfield told Newstalk ZB Hosking it would have been nice for the case numbers to be lower, but they were all connected to current cases or were in managed isolation which is why the government was comfortable announcing the alert level change for Auckland.

Despite that, he said of the alert level change: "You lose a bit of sleep over them."

He also stood by the government's elimination strategy and said the aim was still to get the number of cases back down to zero.