The government is rushing to track the source of the latest Covid-19 cases though officials warned that more infections were inevitable.
New Covid-19 cases in New Zealand’s biggest city of Auckland reached 17.
On Tuesday, the country’s record of 102 days being Covid-free came to an abrupt end after four family members were confirmed to have contracted the novel virus.
At the time, National Health Chief Ashley Bloomfield said that there were 13 new confirmed infections in Auckland though they were all linked to the four infected family members.
The surge in new cases raised the prospect that a three-day lockdown imposed in Auckland since midday Wednesday would be extended as teams of health workers hunted for the cluster's origin and ramped up testing in the city.
Bloomfield said among the new cases was a student at one of New Zealand's largest high schools, attended by more than 3,000 children.
Prime Minister Jacinda Ardern said there were likely to be more cases linked to the recent spike.
"As with our first outbreak, things will get worse before they get better," she said in a televised address.
Ardern was encouraged by the fact that all the cases so far were in a single cluster limited to Auckland.
"You can see the seriousness of the situation," she said.
"While it is serious, it is being dealt with in an urgent but calm and methodical way."