"This case represents an unacceptable failure of the system. It should never have happened and it cannot be repeated," Prime Minister Jacinda Ardern said.
New Zealand recorded two new coronavirus cases after three weeks of no cases, in a situation the prime minister called "an unacceptable failure of the system".
The two women, family members and New Zealand citizens, had travelled from the United Kingdom and were in a managed isolation facility in Auckland upon arrival.
They were allowed to travel to Wellington on "compassionate grounds" via a private vehicle to attend a funeral, said Dr Ashley Bloomfield, New Zealand's director general of health. The women were tested for coronavirus at a drive-thru testing centre in Wellington.
Prime Minister Jacinda Ardern said this case proved the need of a rigorous system at the border and appointed a military leader to oversee quarantine and managed isolation facilities.
"This case represents an unacceptable failure of the system. It should never have happened and it cannot be repeated," Ardern said, emphasising that people returning to New Zealand would need to be in controlled government quarantine.
She added that the country would suspend compassionate leave from quarantine.
"The risk to our collective efforts to eliminate COVID are simply too great. I cannot allow the gains we have all made to be squandered by processes not being upheld," said Ardern.
New Zealand's health ministry has determined 320 potential contacts of the two women. All of them will be contacted by public health officials and encouraged to get a test.
Those who are being quarantined after arriving from overseas will also now be tested twice: on day three and on day 12 of the 14-day isolation.
These include people who were in the same quarantine facility at a hotel in Auckland as well as people who were on a flight from Brisbane, Australia to Auckland.