"These are people who have returned to New Zealand recently and who have become symptomatic, been tested and been confirmed as having COVID-19," he said.

"Most of the remaining cases are close contacts of a previously confirmed case or are associated with an event where there were confirmed cases already."

Two cases of coronavirus in New Zealand are being treated as community transmission - one in Auckland and one in Wairarapa. Contact tracing for all cases is ongoing, he said.

"Across all cases there are currently two where we can not be certain where the infection came from and we are therefore treating them as community transmission," Dr Bloomfield announced.

"We have expected and indeed want to find any cases of COVID-19 in New Zealand. We have expected them because we have had people returning from a range of places around the world that have higher rates of COVID-19 and the important thing of course is that we find these cases, we isolate them, we identify close contacts and we isolate those people."

Authorities are working to increase the capacity of Healthline, and Dr Bloomfield says the Ministry of Health has enough staff to do sufficient contact tracing.

"We have anticipated this increase in cases and in addition to the capacity that there is in all our public health units we have stood up a team here in the ministry that is able to supplement the public health units," he said.

"It can manage at the moment up to 50 new cases a day in addition to that public health unit capacity and is also scalable up as we need it."

The Prime Minister would give an update on the alert level later on this afternoon, he said. The alert level would be "a result of and informed by those cases of community transmission".