Prime Minister Jacinda Ardern ordered the three-day lockdown for Auckland after a couple and their daughter tested positive in the nation widely hailed for virtually eliminating the spread of the contagion.
After meeting Sunday evening, the country's Cabinet chose to move Auckland to Alert Level 3 - the country's second-highest alert level - for three days.
"While the country is at elevated alert levels, Air New Zealand will be taking extra precautions to keep its staff and customers safe".
Victoria's COVID-19 testing boss Jeroen Weimar said the Holiday Inn worker, her partner and housemate as well as the three-year-old child and woman in her 50s were among 38 people who attended the event.
"Customers who are unable to manage their booking online do not need to contact Air New Zealand immediately or prior to their flight's departure - assistance will be provided at a later date to find an alternative flight option or a credit note can be arranged".
The Ministry said contact tracing had identified 10 close contacts outside the household.
On Saturday, Director General of Health Ashley Bloomfield said a person tested positive for the virus while in mandatory isolation died after being moved to North Shore Hospital in Auckland. Six of the close contacts have returned a negative test and four results still pending.
"An intensive source investigation around the latest cases continues, along with public health actions and alert level changes outlined yesterday, are created to break any potential chains of transmission".
Officials are hoping to rapidly trace and test people at the woman's workplace - where she handles laundry from worldwide flights - to find the chain of transmission.
He described the cases as new and active. "But as we have kept saying, there is no such thing as no risk".
The lockdown is the second time Auckland has undergone the emergency measures since a more stringent 51-day nationwide lockdown past year which resulted in New Zealand eliminating the virus. Travel to and from the city is restricted to essential only.
The rest of the country now goes to Alert Level 2 for the same amount of time.
Ardern told Newstalk ZB's Mike Hosking today that the link to the British variant had led officials to think the virus might have come through airport transit or it had stemmed from an worldwide airline crew member.
The move pops the trans-Tasman travel bubble that let people fly between Australia and New Zealand without having to spend 14 days in hotel quarantine.
"The other possibility is global airline crew".
Victorian Premier Daniel Andrews said he spoke to Ms Ardern about a flight that arrived in Victoria from New Zealand on Sunday with 152 people on board.