No immediate changes to alert levels - Ardern

There will be no change to alert levels in Auckland or the rest of New Zealand, Prime Minister Jacinda Ardern has announced.

The reason for no immediate changes was the continued emergence of some mystery cases and the chance that cases could still leak out of Auckland, Ardern said.

Ardern said Cabinet had agreed in principle to move Auckland to alert level 3 at Tuesday next week at 11.59pm. This would be reassessed based on the current information.

Level 2 would remain in place for the rest of New Zealand until the same time, and would also be reassessed by Cabinet based on the latest information.

Cabinet met this afternoon to decide on any alert level changes, as 33 new community cases were announced - all in Auckland.

It is the highest number of daily cases in several days.

However, just one of those cases was at that time yet to be epidemiologically linked to the outbreak (meaning no person-to-person link with prior cases) had been established.

That case was a person who presented to Middlemore Hospital on Saturday. However, their seven other household members have also tested positive and are linked.

Experts say the number of mystery cases, of which there are now 28, is a key factor that could prevent Auckland moving out of lockdown.

While many of them are expected to be resolved, Prime Minister Jacinda Ardern said on Sunday there remained a "handful" - including those who visited Middlemore, some of whom were asymptomatic - of sufficient concern.

Ardern and director-general of health Dr Ashley Bloomfield will front the press conference at 4pm to announce Cabinet's alert-level decision.

Today's cases took the outbreak to 9555 overall - 938 in Auckland and 17 in Wellington.

The outlook for Auckland last week indicated a slim chance of no more spread outside of people's bubbles by this week, but this changed after four cases visited Middlemore Hospital, sparking a series of new cases.

While case numbers remain low and contained, experts warn lifting Auckland out of lockdown too soon could risk reigniting the outbreak.

Those cases are also well spread across the city: Mt Eden, Mangere, Massey, Favona, Papatoetoe, Otara and Manurewa.

There are eight epidemiologically linked subclusters - the two largest subclusters are the Māngere church group (381) and the Birkdale social network cluster (76).

Nine subclusters are not epidemiologically linked.

There are 21 people with Covid in hospital and four in ICU.

Seven of yesterday's 20 cases had exposure events. The other 13 were in isolation throughout the period they were infectious.

Some 8657 Covid tests have been carried out in the last 24 hours - and almost half of those have been in Auckland.

There were no unexpected wastewater detections in the past 24 hours.

While the Government has previously said it would not necessarily wait until there were zero cases in the community before moving alert levels, it has been concerned by the number of unlinked or "mystery cases" popping up.

Deputy Prime Minister Grant Robertson told Newshub this morning he didn't believe there was wide community transmission in Auckland, but said there were a "handful of mystery cases" that were concerning and officials needed to know just how widespread they were.

Level 4 was tough, but it was the best chance of getting on top of the virus and breaking the chain of transmission, he said.

"That is happening, but there are still a few cases at the edges."

He promised the Government would to make sure it laid out a very clear plan for Aucklanders this afternoon.

Epidemiologist Professor Michael Baker told TVNZ this morning he thought it was too early for Auckland to move out of level 4, and doing so could see new Covid cases flaring up again.

He said the mystery cases could prove to be a problem in that they could easily spark up other clusters.

"The trouble is these are people we don't know about.

"This is the end of the outbreak in Auckland and we just have to persist for a few more days."

Pacific health expert Dr Collin Tukuitonga told TVNZ this morning he also felt it was too early for Auckland to come out of alert level 4 based on the new and mystery cases still popping up in the community.