There are four further deaths linked to Covid-19 and Director General of Health Ashley Bloomfield says it is a "sobering reminder" of what's at stake in the fight against the pandemic.
And he has confirmed that the mystery cluster in Auckland linked to a private event was a stag party, but he would not say how many people had attended.
One man in his 70s has died in Wellington - a case linked to overseas travel - and three from the Rosewood rest home cluster in Christchurch have died, including two men in their 90s and a man in his 80s.
They were all confirmed cases of Covid-19 and had underlying health conditions, Bloomfield said.
"We have previously signalled the underlying vulnerabilities of the Rosewood residents and that this group would continue to be at risk. That does not make today's news any less sad.
"This is the largest number of deaths we have recorded in any day in New Zealand from Covid-19 and it is a sobering reminder of what is at stake."
The Covid-19 death toll is now nine, including six from the Rosewood cluster, but despite the sad news, Bloomfield said New Zealand appeared to be past its Covid-19 peak.
He said he had lost his two parents and knew how hard it would be to have access to loved ones denied, and the blanket ban on visiting people infected with Covid-19 was being reviewed.
The processes around the six aged-care residential facilities and rest homes where Covid-19 has been detected, including how visits were allowed, were also being reviewed to learn any relevant lessons.
There are 17 new cases of Covid-19 to report since yesterday - made up of eight new confirmed cases and nine new probable cases.
There are 628 cases that have recovered, an increase of 82 from the previous day.
Bloomfield said New Zealand has passed the peak of new cases, but warned the public against any complacency.
"It was important to know now where new cases come from, and then to ring-fence them by using comprehensive contact-tracing," he said.
There are 1366 cases in New Zealand, with 15 cases in hospital; three were in ICU, with one case in Dunedin in a critical condition.
Of all the cases, 48 per cent were linked to clusters, 39 per cent linked to overseas travel, and 2 per cent were due to community transmission.
And he confirmed that the Bluff wedding cluster started from someone linked to overseas travel, but he said he did not have enough information to comment on whether it had been an Air NZ flight attendant with symptoms.
Bloomfield rejected the suggestion that patients at Burwood Hospital - who were moved from Rosewood when the rest home got a coronavirus case - had been essentially left to die.
The residents in Burwood are receiving the same treatment as they would have in Rosewood, he added.
The two new fatalities in Burwood were not treated in ICU, and he said that would have been a decision made by those families in conjunction with health experts.
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He relayed some feedback from a Rosewood family, who praised the staff there and were thankful to have Skype contact with their loved one.
Bloomfield said families were not allowed to visit their loved ones with Covid-19, not just the elderly, but that was currently being reviewed.
The blanket ban on visiting those with Covid-19 was in place to break the chain of transmission, he said.
"As someone whose parents have passed away, I absolutely understand how people must be feeling and that is why we are looking specifically at that policy."
Coming out of lockdown
He said the ministry would provide "robust" advice to Cabinet for its decision on Monday on whether to lift the lockdown, and he was awaiting more information on contact-tracing before Monday.
Earlier today top epidemiologist Sir David Skegg said Cabinet would be playing "Russian roulette" with New Zealanders' lives if it made its decision before improving contact-tracing and before surveillance testing had been widely undertaken.
Australia was now able to do all necessary contact-tracing for new cases within two to three days, but Bloomfield had told the committee he was awaiting further details before he could say how long the process took in New Zealand.
He later told media at a press conference that the Health Ministry could already contact-trace within two to three days of any new case, but he wanted that capacity to be reached for a higher volume of cases.
There were 220 staff available to contact-trace, and about 100 cases could be traced per day. The number of new cases everyday was also shrinking, and the number of close contacts per case was about four to five, he said.
The use of an app to enhance contact-tracing would only help if there was 80 per cent voluntary take up of the app, he added.
Surveillance testing was still yet to get underway, but Bloomfield said the testing data that the Ministry had released showed that only two regions - Whanganui and Te Tai Rawhiti - needed more testing to ensure there weren't' any undetected outbreaks.
Aged care review launched
A review of aged residential care facilities that had been infected would also be conducted, he said.
"My hope is to do this in conjunction with the Aged Care Association."
"We know that aged residential care and settings are very vulnerable if we get Covid-19 in those facilities," Bloomfield said.
Working closely with those facilities and acting quickly and preemptively was vital, he added.
There were 650 such facilities nationwide, and the relatively low number of cases in those facilities was an indication of the care and preparation measures across the sector, including "no visitor" policies before the lockdown was implemented.
Every new arrival goes into isolation for 14 days, Bloomfield said, and there are no shared meals.
He said there was a "low threshold" for testing in those facilities, but he has not taken up the call from the sector to test every new arrival - about 700 every day.
Bloomfield said more actions were being looked at and more funding for the sector would be announced later this week.
"We continue to work with them to ensure we are maximising the value of testing."
He would not name the latest rest home in Auckland where there was now a cluster, but he added half of the cases were in the rest home and half were in the community. It was unclear at the moment where the index case was.
Yesterday there were 1572 tests conducted, and the seven-day rolling average of tests is 3039; 64,399 tests have been undertaken so far.
There were expected to be a lower number of tests over the Easter break.
There had been a lower number of tests in Australia too, Bloomfield said, but he added that a low threshold for testing anyone with respiratory symptoms would stay in place.
Asked about a nurse at Burwood Hospital working without hair protection or foot covers, Bloomfield said he couldn't comment on the specifics of that case.
But he added that the workers there should have access to all the PPE they needed.
Yesterday Prime Minister Jacinda Ardern reminded people to continue to be vigilant and follow lockdown rules, otherwise the first half advantage that New Zealand had worked hard for would be wasted.
She reiterated that New Zealand would not be coming out of level four early and border restrictions would be in place for "a long time to come".
She will give a post-Cabinet press conference today at 4pm.
Next Monday Cabinet will decide whether New Zealand will drop to alert level three on from April 23.
Ardern will outline what life under alert level 3 will look like on Thursday this week.