The Herald understands ED nurses were told they should still go to work, as the person who later tested positive was vigilant and wore PPE when on site.
More detail will be provided when available.
Meanwhile, about two-thirds of people infected in New Zealand's Delta outbreak are younger than 30 and half come from the Pasifika community.
The new insights - which one Pacific health expert has called "depressingly familiar" - come as the outbreak swells to nearly 150 cases.
The ministry data showed that, of 148 cases confirmed between August 17 and August 23, and which had been verified as not being linked to overseas travel, 47 were aged between 20 and 29.
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A further 32 cases were aged between 10 and 19 and another 14 were aged under nine.
Of the remainder, 10 were in their 30s, another 13 were in their 40s, 19 were aged in their 50s, nine were in their 60s, three cases were in their 70s, and another single case was in their 80s.
The majority of 41 new cases announced today were household contacts of existing cases or people who had been at known locations of interest.
Meanwhile nine students at AUT in Auckland have now tested positive for Covid-19.
The university this afternoon said it was aware of nine confirmed cases, but of those people, one was not on campus while infectious and further information was being sought on three other students.
AUT has another 14 locations of interest today, bringing the total to 29 locations.
RNZ reports the University of Auckland is not aware of any more of its students testing positive for Covid-19. A student at one of the university's halls of residence has the virus and anyone in the Whitaker and Waipārūrū Halls was told to isolate and get tested.
The university says pop-up testing centres there over the weekend have now gone.
It understands all students were tested and so far they haven't been advised of any more cases.
Director general of health Dr Ashley Bloomfield said about 50 per cent of cases in the outbreak were of Pacific ethnicity, largely as a result of the sub-cluster of about 58 cases linked to the Assembly of God Church (AOG) of Samoa in Mangere.
Bloomfield said he recognised concerns about Māori and Pasifika communities, given these groups often had higher rates of pre-existing health conditions.
Dr Debbie Ryan, of Pacific Perspectives, said reports that Pacific people accounted for more than half of the cases in the outbreak - yet just 7 per cent of the population - were "depressingly familiar".
Pacific people made up nearly 60 per cent of the community cases in the August 2020 Covid-19, and more than 60 per cent of the measles cases in the 2019 outbreak that affected more than 2000 children and young people.
"No doubt we will get through the current crisis. Pacific communities and health providers and health workers have again pulled together brilliantly to do what is required," Ryan said.
"But we need a circuit breaker to address these unacceptable disparities."
Bloomfield said health authorities and the Pasifika community were working together on contact tracing.
"We will make sure that we get rid of Covid in that community."
The second-largest sub-cluster was centred on Birkdale, on Auckland's North Shore, and had about 23 known cases.
More than 9000 contacts had been contacted and were self-isolating, while almost 900 frontline contact-tracers were working on the pandemic response.
The Ministry of Health has this evening released another 15 new locations of interest including Auckland's Aotea Centre.
There are now 450 visits to 338 locations.
New locations include:
Aotea Centre Auckland; Bus NB5021 487 Dominion Road to 37 Symonds Street; TAPAC The Auckland Performing Arts Centre Western Springs - Foyer; Countdown Auckland Metro, 19-25 Victoria Street West, Auckland CBD, Auckland 1010; Break Time Symonds Street, 43 Symonds Street, Grafton, Auckland 1010; Vmart Diray 79 Wakefield Street, City, Auckland 1010; Bus NB2118 84 Wakefield Street stop to 510 Dominion Road stop; Subway Auckland CBD; MECCA MAXIMA Westfield, Albany; Unichem Pharmacy
Countdown Pakuranga; Bus NX2 Akoranga Station to University of Auckland stop 7039 Mayoral Drive; 24/7 Breaktime Symonds Street; TAPAC The Auckland Performing Arts Centre Western Springs - VIPERS class; Assembly Of God Church of Samoa Mangere
Meanwhile, police have arrested a Christchurch man after he failed to wear a mask and was aggressive towards supermarket staff. He is due to appear in court on Friday.
Police have received a total of 1394 phone calls by members of the public reporting Covid-19 breaches.
Since Alert Level 4 came into place, 44 people have been charged.
Earlier, Bloomfield said officials were already dealing with 10 times more contacts than there were during last August's outbreak.
The 41 new cases, of which 38 were in Auckland and the rest in Wellington, followed the 21 announced on Sunday and the 35 disclosed yesterday.
Bloomfield and Deputy Prime Minister Grant Robertson told reporters they expected more new active Covid-19 cases in days ahead, and it could be several days before case numbers peaked.
"We're not there yet," Robertson said.
Earlier today, Otago University epidemiologist Professor Michael Baker told the Herald that New Zealand could hope for a peak halfway through this week.
"We don't know how many cases we really started with when we went into lockdown and how many were incubating," Baker said.
"If you look at the likely incubation periods, there's a little bit of a delay with lockdown as people returned to their homes, developed symptoms and then infected people in their households.
"So we're still seeing that effect - and that should start to diminish now."
Baker said it would be useful to see the Government classify cases as those that were in the community before lockdown, those that had been detected while at home, and those that were among essential workers still operating under alert level 4 - data that Bloomfield said officials were in the process of providing.
"What we really want to know is if there are any unsuspected cases occurring in the community that don't have a connection to cases reported now, which could suggest some leakiness in lockdown," Baker said.
Delta spreading among essential workers was something that mired attempts to bring New South Wales under control although Prime Minister Jacinda Ardern said there were no indications of that happening yet.
Baker's fellow Otago epidemiologist, Professor Nick Wilson, said New Zealand should have a "much better idea" of the outbreak by Friday, with tools like wastewater surveillance, community testing and genomic analysis informing the picture.
"With all of those things, we should hopefully be able to rule out there having been a large super-spreading event that we don't know about, or that there's been major spread among essential workers," Wilson said.
"But I think at this stage, it's relatively reassuring that we will achieve what Queensland, South Australia and China have done, and stamp out a Delta outbreak."
Earlier, Te Pūnaha Matatini modeller Professor Shaun Hendy said the cluster now clearly reaching towards the upper limit of expectations when it was detected in Auckland nearly a week ago.
Then, they predicted 50 to 120 cases to have been circulating prior to the lockdown.
Hendy said a "best-case scenario" could see about 200 cases - greater than the outbreak in August last year - while it was possible the cluster could swell to 1000.
"It's very early to be making estimates because we don't yet know how effective alert level 4 is, but it is possible we could see 1000 cases before we close out this cluster.
"This does mean we will likely see level 4 held in place for several weeks more in the Auckland region.
"For the rest of the country, we will have to wait until later in the week to see if they remain clear, in which case, an alert-level shift could be considered on Friday."
