Health officials are scrambling to trace the contacts of two Papatoetoe High School students who have just tested positive for Covid-19.
Meanwhile, ESR testing of wastewater has so far found "no evidence of any community cases of Covid-19", the Ministry of Health says.
The new cases are students - a brother and sister who attend the school, which is now closed until at least Friday.
The sister is a classmate and close contact of the original case who tested positive last week.
Interviews were continuing with the latest infected pupils, the Ministry said in its latest Covid update at 1pm.
Case investigation and contact tracing for the latest cases were currently underway, said the ministry.
As at 11.30am, 31 close contacts and 1523 casual plus contacts had been identified at Papatoetoe High School. Contact tracing had identified 128 close contacts associated with the original family at the centre of the Covid outbreak. Of these, one had tested positive (one of today's new cases), 76 had tested negative, and 49 results were still being analysed.
More information, including any locations of interest, would be revealed at a media conference at 4.30pm when Prime Minister Jacinda Ardern is due to announce Cabinet's decision on alert levels.
The first results from ESR's wastewater testing undertaken in February had come back.
The ministry said they had found "no evidence of any community cases of Covid-19" in wastewater sampled.
The results included:
• Auckland Western and Eastern Interceptors, North Shore (Rosedale), Rotorua, and Christchurch all returned negative.
• The South Western Interceptor (Auckland) returned a positive result, which is a consequence of Covid-19 cases at the Auckland quarantine facility. The levels detected are consistent with those seen over the last month.
However, samples collected from the Papatoetoe catchment area arrived just this morning and were being processed today.
Hamilton samples were also being processed today.
Further results would follow as they were received and tested throughout the week.
Testing across Auckland's 10 community testing stations remained steady today, with no significant wait times, the ministry said.
"We want to thank our Auckland communities for getting tested – since Sunday, more than 20,000 tests have been performed in the community."
"We would like to thank the public for their patience while teams work tirelessly to test everyone who needs a test," the ministry said.
The ministry said all community testing centres in the metro Auckland experienced a big increase in demand for testing yesterday.
As at 11am today labs in metro Auckland had registered 7,010 tests from yesterday and this number was expected to increase throughout today.
Laboratories across the Auckland region were coping well, with the current turnaround time for test results 48 hours. Extra staff had been rostered on to help manage any surge in the number of tests needing to be processed, said the ministry.
The single case detected at the border was a person who arrived from Kazakhstan on February 14. The infection was detected on day 0/1 routine testing.
The person is now in quarantine in Auckland.
There are now 49 active cases in New Zealand.
The total number of confirmed Covid infections since the outbreak began almost a year ago is 1,984.
On Tuesday laboratories processed 17,439 tests.
To date, there have been 1,613,211 Covid test processed since the infection hit our shores.
The ministry said there were more than 1,024,397 poster scans recorded since midday yesterday.
This afternoon Covid Response Minister Chris Hipkins revealed two more young people had tested positive for Covid, bringing the latest Auckland cluster to five.
Since midnight Sunday the Auckland region has been in an alert level 3, as health officials grapple with the source and extent of the latest outbreak which has started with three people in one south Auckland family.
The cause of the outbreak is stumping health officials with no genomic link to any strain seen in New Zealand to date. It is still not clear which member of the family - the mother or daughter - first contracted the virus.
The Auckland region, where there are now five confirmed cases of Covid in the community, is currently under a lockdown with no movement out of the region unless with a permit, no large gatherings and residents asked to stay at home, only leaving for essential supplies. The rest of the country is at alert level 2.
Since Sunday's midnight lockdown there were no new cases in the community for the first two days despite widespread testing in Auckland and Taranaki where infected members of the family travelled for a long weekend break.
This morning Covid Response Minister Chris Hipkins told Newstalk ZB's Mike Hosking he was "optimistic" the three cases within one family had been contained but was not prepared to pre-empt any Cabinet decision to downgrade the alert.
At the time he said there had been no positive cases that he'd been made aware of overnight.
"We'll get the overnight bench testing results about nine o'clock this morning as they normally come in and the fact that we haven't been notified of any new cases is very encouraging. Our goal here was a short, sharp response. It looks like at this point like that's been effective. We'll have more information as the day unfolds but I'm optimistic at this point."
Asked by Hosking if another day of zero cases meant the country was done and could get out of the alert levels, Hipkins said: "I wouldn't go that far - there's still a few pieces of the puzzle that Cabinet will want to weigh up including the fact that we haven't got a confirmed source for this group of cases."
Meanwhile, experts are debating the Government's next moves, with one prominent epidemiologist urging caution - a move to a level 2.5 for Auckland - while one economist/modeller believes concerns over a community outbreak have been a possible "false alarm".
The 19-year-old disappeared without her wallet or mobile phone.