Health officials have announced another 13 confirmed cases of COVID-19 in New Zealand, bringing the total to 52.

Two of them have yet to be linked to travel from overseas, meaning they are possible examples of community transmission - one in Auckland, one in Wellington.

Director-General of Health Ashley Bloomfield made the announcement at 11am on Saturday.

"Most of these cases are travel-related, but as yet in two instances, no link to overseas travel has been ascertained, and we continue to investigate. At this point, we cannot rule out a risk of community transmission in these cases.

"We always knew that cases apparently not linked to travel would happen, and we are prepared for that."

He said contact tracing was underway for all the new cases, and any contacts would be required to go into self-isolation.

In the Auckland case, Dr Bloomfield said the partner of the patient has "a lot of contact with overseas travellers in the course of their work". The partner is being tested, but the results aren't yet available.

Of the new cases, four are in Wellington, one in Taranaki, three in Auckland, one in Waikato, one in Taupo, one in Manawatu and two in Nelson. The Celebrity Solstice cruise ship also had one confirmed infection of a New Zealander on board.

Three people infected with the virus remain in hospital - one in Queenstown, one in Nelson and one in North Shore. All are stable.