Two new cases were found on Wednesday after mass testing of students at Papatoetoe High School.

A third fresh community case, a family member of one of those students, was announced by Director General of Health Ashley Bloomfield later on Wednesday.

Prime Minister Jacinda Ardern ordered the lockdown on Valentine's Day after the emergence of three cases, all from one family, including a Papatoetoe High student.

Ms Ardern called the six cases in four days "good news" that made her confident enough to move down alert level settings.

"We believe this to be a small contained outbreak with the evidence we have to date," she said.

Auckland will shift from alert level three to two, while the rest of New Zealand will shift from alert level two to one.

Alert level two involves enhanced mask-wearing, caps on gatherings and social distancing, while alert level one is essentially pre-COVID life.

The decision to end Auckland's lockdown just hours after the discovery of new community cases is one of the riskier moves of Ms Ardern's stewardship during the pandemic.

The Labour leader has become synonymous with a health-first approach through the crisis, an approach which has kept New Zealand's death toll to just 26.

"We don't have a widespread outbreak, but rather a small chain of transmission which is manageable by our normal contact tracing," Ms Ardern said.

That contact tracing has seen thousands of people move to home isolation and more than 23,000 people get tested.

Dr Bloomfield said while his team had not discovered the source of the outbreak, it was encouraging the new cases "were in a tight configuration with clear epidemiological linkages".

"It is reassuring that they are all linked," he said.

The decision clears the Australian T20 tour of New Zealand to begin on Sunday in Christchurch.

New Zealand's cabinet will make a new assessment on alert level settings on Monday.

Australian Associated Press