The source of Auckland's latest COVID-19 cluster still remains elusive as health officials continue to probe, and then cross off, possible scenarios that may have caused the transmission.
One of the strongest leads has now also hit a dead end, with no sequenced genomes in the international database matching those of the three Papatoetoe cases.
Genomic sequencing has confirmed there is no connection between the new infections and cases recorded in New Zealand's managed isolation facilities, ruling out the possibility that the virus was contracted from a new arrival or breach of the system.
One of the three initial cases is an employee in the laundry department of the Auckland Airport LSG Sky Chefs, a flight catering facility. Although the woman does not have contact with new arrivals, officials have theorised that an international aircrew member - or a transit passenger who failed to remain airside - could be plausible explanations for the transmission.
However, Associate Minister of Health Dr Ayesha Verrall said on Thursday that efforts to link the latest cluster to an overseas infection had so far proved unsuccessful.
"One of the key pieces of information is we haven't found a match between these cases and any case that was in the managed isolation system, using the genome sequencing data that we have," Dr Verrall told The AM Show.
"That prompted us to think if it could have been an overseas [air]crew member on a flight who came, infected someone, and then left, and maybe that's why they're not on our database of sequenced [returnees].
"So we looked at [people in managed isolation] overseas to see if it matched, but unfortunately, we haven't found plausible matches there either."
Dr Verrall reiterated that it's still correct to assume the virus was imported into New Zealand through the border, and has not been circulating in the community undetected.
Speaking to The AM Show on Wednesday, COVID-19 Response Minister Chris Hipkins said that in regards to the source, health authorities "may never nail it down".
Dr Verrall echoed that on Thursday, saying that although it's unsatisfying, the answers can sometimes remain a mystery.
"It is unsatisfying [when] we don't find the answers, but I'm afraid that's the way these case investigations often go," she said.
Dr Verrall also said the implementation of level 3 restrictions in Auckland was justified, as the Government was confronted with a "very unclear set of circumstances".
The region was plunged into a provisional three-day lockdown at 11:59pm on Sunday after it was revealed that a mother, father, and daughter in Papatoetoe had tested positive in the community.
"On Sunday, we were confronted with a very unclear set of circumstances, with a case that was not clearly linked to the border, she was in a workplace where she didn't have direct contact with new arrivals," Dr Verrall said.
"Remember, the mother and daughter had an onset of symptoms at about the same time, which suggests that they could have been infected by a third person. That was what worried us about the possibility of community transmission."
However, the inability to pinpoint a source has experts doubting the Government's decision to shift Auckland to alert level 2 after just three days under level 3, with some expressing concern that additional cases may have gone undetected.
However, Dr Verrall appeared confident there are no unidentified chains of transmission in the community.
"I think it's a really good use of the alert level system, to use it in a short, sharp way to assess whether there's community transmission," she said.
"Now, three days later and 22,000 tests later, we can see that we've excluded that possibility."
Three new community cases were reported on Wednesday. All are connected to the original trio from the weekend and there is no evidence - from either community testing or wastewater testing - of any wider transmission so far.
One of the new cases (referred to as Case D) is a classmate of the daughter (Case A) at Papatoetoe High school. The other two are within Case D's household.