The Government is "ploughing ahead" with Auckland's move out of lockdown and into level 2 at 11.59pm tonight, the Minister of Health says.
Chris Hipkins has revealed there will be slightly fewer cases announced today, compared with the 13 yesterday - 11 of them in the community.
All risks were being weighed up, he said.
"We're still ploughing ahead with level 2 today," Hipkins told Mediaworks. "The key thing for us is looking at that cluster - are all the cases, within the cluster, are they known and identified? The evidence so far is yes, they are."
Asked how many daily cases would lead to a return to level 3, Hipkins said it depended on their nature.
"This is one cluster with a bit of a strong sub-cluster building around it. They're all people, by and large, who we've known about and been in isolation," he told Mediaworks.
He said tonight's move was more a transition to a level-2.5, with masks mandatory on public transport and limits on the numbers of people able to gather socially.
He confirmed the source of Auckland's outbreak had not been found. "Every new piece of the puzzle helps to paint a bit more of a picture of where it might have come from," he told Mediaworks.
Auckland is due to come out of level 3 lockdown at 11.59pm tonight - PM Jacinda Ardern will hold a press conference today to confirm the move, but experts are calling for a rethink as new cases of the virus across the city show no sign of slowing down.
It comes as the Government appears to be widening its testing net, with an "important message" posted on the Government's official Unite Against Covid-19 Facebook page last night, encouraging people in west and south Auckland to be tested.
Ardern will confirm at 1pm today whether Auckland's Covid-19 restrictions will be relaxed and the region can move to level 2 tonight as planned. The press conference will be broadcast live on nzherald.co.nz and Newstalk ZB.
The move, announced last Monday, is looking increasingly risky after 13 new Covid cases were reported in the city yesterday - the highest for almost two weeks.
Auckland University Professor Shaun Hendy called on the Government to reconsider the planned move down to Covid alert level 2.
University of Otago Professor Michael Baker called for a tough "alert level 2.5" with everyone wearing masks in schools, indoor workplaces and other indoor gatherings, as well as the planned maximum of 10 people in gatherings in Auckland.
The Ministry of Health has now reported 135 cases of community transmission since the first four cases in the Auckland cluster on August 11, including 11 new community cases and two more in quarantine facilities yesterday.
But Ardern's office played down the fears, saying: "As noted earlier this week, there was an expectation of additional cases from the cluster."
Last night, a post on the Government's official Unite Against Covid-19 Facebook page was titled: "Important message - if you're in South or West Auckland, please have a test".
It further read: "If you develop symptoms consistent with Covid-19, have a test. If you're in South or West Auckland, or if you have a greater risk of poor health outcomes if you were to get Covid-19 even if you don't have symptoms, please have a test."
A reply from an administrator to a question on a post urging the testing stated: "Widespread testing remains a critical part of eliminating Covid-19 in our communities."
The combined populations of West and South Auckland are an estimated 500,000.
The Ministry of Health said 10 of the 11 new community cases yesterday were clearly linked to the Auckland cluster - six associated with the Mt Roskill Evangelical Church and four others who were contacts of previously reported cases.
"The remaining person who has tested positive for Covid-19 is being interviewed today [Saturday] to determine their possible links to the cluster," the ministry said.
Hendy, whose modelling has guided the Government's response to date, said it was a concern that some people were still presenting to health services with Covid symptoms without being picked up by the teams tracing all close contacts of people already known to have the virus.
"That suggests that we are not completely ahead of this cluster," he said.
New daily cases trended downwards on a seven-day moving average basis from a peak of 10.6 a day in the week up to August 18 to a low of 5.1 a day in the week to last Tuesday, August 25.
But since then the seven-day average has crept up again to 5.4 a day in the week to Friday August 28 - a sharp contrast to New Zealand's first experience with the virus when cases rose steeply to a peak of about 90 cases a day in early April and then fell equally sharply to zero cases on most days from mid-May.
Hendy said Auckland's level 3 "lockdown lite" was never going to contain the virus as effectively as the full level 4 national lockdown from late March to early May.
"That is the trade-off. If you are at lower alert levels, it takes longer for those numbers to drop away," he said.
"We know that level 2 is not really designed to contain a community outbreak. Level 2 definitely runs the risk of the outbreak starting to grow again."
Hendy said ministers should reconsider moving Auckland to alert level 2 on Monday - and if the change still goes ahead, employers should keep workers at home if possible.
"If you can work at home, you should continue to do so for the next few weeks," he said.
He said reopening Auckland schools on Monday was "certainly a concern".
"We need schools to be keeping social distancing in place and making sure that they keep good records of who has been in particular classes," he said.
Asked whether schools should stay closed for longer, he said: "I think it's something we should consider. There are lots of tradeoffs in that decision. Obviously that puts stress on families if they are having to supervise children, so I think it's about finding a mix of things that keep level 2 with that reproductive number below 1."
Baker said the latest cases would have caught the virus after level 3 restrictions were imposed, so "we need to be doing more, rather than less, to stamp it out".
"Going down to level 2 on Monday means it's more likely we will start to see numbers at the very least not decrease. We'd have a very prolonged transmission and there will be some risk of the numbers starting to track up," he said.
"Basically we need to throw something out there to stop the virus, and from where I sit the only available thing is mass masking.
"If you have a level 2.5, which sets a gathering size of 10, and if you add masks it's more effective, so you are going to have a requirement of mass mask use in all indoor environments including public transport and including workplaces, schools and social meeting places."
A former director of public health Dr Collin Tukuitonga said he supported wearing masks and limiting gatherings, but Ardern would have to make a call after today's numbers are available.
"If say we had 12, and we can connect them all to the existing cluster, I would be relaxed about going to level 2 with those other measures," he said.
"However, say there's 12 and two we can't link to the church or to the original cluster, I would be questioning the wisdom of going down to level 2, because that tells me that there are other sources in the community that we don't know about."
Helen and Ian Burgess, Todd Clark, Sandra Matthews, Dr Beata Bukosa, and Damien O'Connor.