Health officials are struggling to identify the source of Auckland's three community cases, with COVID-19 Response Minister Chris Hipkins admitting the Government "may never be able to nail it down".
On Sunday, it was announced that three new cases of COVID-19 - a mother, father, and child - had been detected in the community. Genomic sequencing subsequently confirmed the south Auckland family were carrying the B.1.1.7 strain, a highly infectious variant first identified in the United Kingdom.
How the first case contracted the virus still remains a mystery.
Speaking to The AM Show on Wednesday morning, Minister Hipkins said health officials are pursuing a number of different possibilities as to how the transmission occurred - however, each scenario is considered "highly unlikely".
"That's the thing about this particular case - all of our potential sources are looking like they're highly unlikely. We're looking at a bunch of scenarios that are highly unlikely, but possible," Hipkins said.
It was initially reported that the mother - an employee in the laundry department of LSG Sky Chefs, a flight catering facility at Auckland Airport - was the first of the three to become infected.
Yet on Tuesday, Director-General of Health, Dr Ashley Bloomfield, said the daughter - a student at Papatoetoe High School - had been the first to present symptoms, suggesting she may have also been the first to contract the virus.
"Could it have come off the laundry? Highly unlikely, but possible. Could the daughter have picked it up somewhere in the community? Highly unlikely, but possible," Hipkins told The AM Show.
"That's what this investigation process looks at. We may never be able to nail it down, but what we can do - with the extensive testing and contact tracing - is really minimise the risk of further spread, and that's looking pretty good so far."
But Hipkins said he doesn't want to "preempt" that Auckland will be moved out of its provisional three-day lockdown, a response the Government enforced at 11:59pm on Sunday in a bid to curb any potential spread of the virus. No new cases have been detected in the community for two consecutive days, a result both Hipkins and Bloomfield have called "very encouraging".
However, the mystery as to how the first case contracted COVID-19 will play a factor in whether Cabinet will shift Auckland out of level 3, Hipkins said.
He noted that so far, Wednesday "appears to be another good day".
"I'm reasonably optimistic," he said.
The Government will start rolling out its vaccination programme on Saturday, with a small group of border workers set to receive the Pfizer vaccine.
The campaign will ramp up early next week, Hipkins said, with officials aiming to vaccinate roughly 12,000 border staff within a two-to-three-week period.
Contacts of the three cases continue to undergo testing in a widespread campaign targeting close, 'casual plus' and casual contacts, as well as the broader community. Further results of this testing will be revealed on Wednesday, with the latest batch of results from overnight expected at around 9am.