A coronavirus outbreak that sent New Zealand’s biggest city into a snap lockdown over the weekend involved the more transmissable UK variant, health officials confirmed today, the first time the strain has been detected locally.

Auckland’s nearly two million residents were plunged into a new three-day lockdown yesterday after three new Covid-19 cases were detected in the city.

Genome sequencing of two the cases — all three are immediate family — revealed they were the B1.1.7 variant. The source of the cases remains unknown, authorities said, adding they were scanning international genome databases for a match.

“We were absolutely right to make the decision to be extra cautious because we assumed it was going to be one of the more transmissible variants,” Prime Minister Jacinda Ardern said on Facebook Live post on Monday.

The Auckland lockdown is the first in New Zealand in six months, after a hard shutdown early in the pandemic appeared to have largely eliminated local transmission. The country was ranked the best performing nation in an index by Australia’s Lowy Institute of almost 100 countries based on containment of the coronavirus.

The fresh outbreak prompted neighbouring Australia to suspend an arrangement that allowed New Zealanders to enter Australia without serving a 14-day hotel quarantine period.

New Zealand’s health department said today there were no new cases of community transmission, but five in managed isolation facilities.

The country has reported a total of 2,330 confirmed and probable cases since the start of the pandemic, a fraction of those reported by other developed nations, including 25 deaths. Forty-seven cases remained active, health officials said on Monday.

In Auckland, long queues formed outside supermarkets after yesterday’s announcement as people tried to stock up on goods ahead of the implementation of the order that requires them to stay at home except for essential shopping and work.

The Covid-19 alert for the rest of the country was raised up a notch to Level 2, with all gatherings limited to 100 people.