Dr Ashley Bloomfield says a woman in her 20s in the family travelled to Rotorua on Saturday while she was symptomatic, and the ministry is working to find out where the family went in Rotorua.

Prime Minister Jacinda Ardern and the Director-General of Health are giving a briefing with updates on the new Covid-19 cases and the alert level changes.

The government last night announced that four Covid-19 cases of unknown origin had been found in a family in South Auckland. This prompted a move to alert level 3 for all of Auckland from noon today and level 2 restrictions for the rest of the country.

Restrictions will last until at least midnight on Friday, but experts are warning people to prepare themselves for the possibility they will remain in place longer.

A child who attends Mount Albert Primary School is believed to be involved with the community cases.

People in Rotorua and around the country should seek advice if they have symptoms, Dr Bloomfield says. The family had visited some family and tourist locations during their visit there, he says.

Ardern says the whole country has gone to level 2 because the family travelled to Rotorua.

The family are still in isolation at home and the ministry is working with them about possibly going into quarantine, he says.

There are currently testing sites availabe in Rotorua (on Vaughn Rd) and Taupo for people in the area, he says.

No members of the family require hospital care at this stage.

The ministry is testing all close and casual contacts of the family that have come into contact with them recently, which the ministry estimates to be 130 people including workplace colleagues.

Three colleagues of the male and his partner are symptomatic and are isolating, Dr Bloomfield says.

The number of confirmed cases remains four at this point, and "a number" of others have been tested but the results of those is not yet known, he says.

The ministry is using genome sequencing on all those who have tested positive to try and track the source of the virus.

There are 140 people on standby to help from the National Contact Tracing center Auckland health staff, Dr Bloomfield says.

He says the ministry is prepared to test tens of thousands of people over the coming days and that they have capacity to test 12,000 a day currently.

Testing stations in Auckland will be available in Eden Terrace, Northcote, Henderson, New Lynn, Wiri and Ōtara from 8am or 9am until 5pm or 6pm for seven days a week.

Ardern is asking for only symptomatic people in Auckland to be tested and not clog up facilities.

She says the Ministry of Health is working to scale up its testing capabilities over the coming days.

With news of the aged care lockdown, Ardern said the ministry was working with the sector to ensure staff did not work across different facilities.

Under alert level 3, Aucklanders should reform their family bubbles like the previous lockdown and the same restrictions apply as last time apply, Ardern says.

Ardern says businesses can still trade during alert level 3 as long as distancing is maintained and orders are taken over the phone or online.

People should make sure they keep their 2m distancing when out in public.

Ardern says the government is seeking advice from the Electoral Commission on what is happening with the election, but there is no update yet.

The Minister of Health and Dr Bloomfield are asking people in Auckland to wear masks if they were out in public either for essential travel or supermarket shopping.

Chris Hipkins said an order would be issued at midday today and making mask wearing mandatory for Aucklanders was one of the things being considered.