There are unconfirmed reports of another person testing positive for Covid-19 at an Auckland hotel.

It comes as Prime Minister Jacinda Ardern and Newstalk ZB's Mike Hosking go head-to-head over the number of potential people who have left quarantine without being tested - as was the case last week when two women left an Auckland hotel and later tested positive.

The Herald understands a person staying at a Novotel in Auckland tested positive on Sunday night and the hotel is now in full lockdown.

If confirmed, this would be at least eight active cases in New Zealand, all from managed quarantine facilities.

Alexa Cook, who has been in isolation at the Novotel Auckland Airport since June 13, said she was also informed of the new case at 8.25 on Sunday night. "We had a call to our hotel room from reception and it was a guy from the New Zealand Defence Force saying, 'please stay in your room, the hotel has gone into full lockdown because there's been a positive Covid-19 test from inside this hotel'."

She said she wasn't told whether it was one or more cases, just that it "was one bubble".

Two new Covid-19 case discoveries today proves the Government's isolation and quarantine system is working, the heads of the operation say.

On Newstalk ZB today, Ardern could not say how many people had left hotels untested, before protocols were tightened last week. She said the Ministry of Health was still working through the number.

"The most important thing is the 14 days in isolation," she told Hosking. "The 14 days is the most cautious approach. Belts and braces are testing. Fourteen days is how you can be assured if you are symptom free that you are safe."

Since quarantine was introduced, more than 20,000 people had been through facilities, she said. Everyone other than those on compassionate leave had been in the facilities for at least 14 days, she said.

Hosking: You have a major credibility issue around what you say and what actually happens.

Ardern: I am going to dispute that Mike. We are not the only country who are putting in place protocols like this. Many other countries, however, just allow people to self-isolate at home.

Hosking: That's got nothing to do with anything. We have our own programme to run. What you are telling us happens doesn't happen - we found that out last week.

Ardern: Mike, I am of course accepting that what happened last week was not in accordance with the very strict protocol that was put in place. Health will not argue that, I will not argue that. It is why we have put in place someone completely new to oversee testing, the entire process and exit criteria - and that is Air Commodore Webb from the Defence Force.

More than 20,000 had been through quarantine and there was not one case, she said, where someone had passed on Covid to anyone outside of quarantine.

Hosking: You don't know that. You don't know that because they left the hotels untested.

Ardern: Mike, Yes we do.

Hosking: You don't.

Arden: Yes, we do. We do.

Hosking: You do not - they left the hotels untested.

Ardern: Yes... we can know because we have had community testing.

Hosking: That doesn't mean anything.

Ardern: I have made my point - you continue to make yours.

Ardern said there 4272 people in facilities now - double that of last month. "The pandemic is growing but some of the flights are starting to increase. We have more New Zealanders coming home."

This included flights from the India, a country that was experiencing a significant number of cases and now considered "high-risk".

"Kiwis are going to continue coming home and we have an obligation to allow them to come home."

Rigorous testing was continuing and there were tight protocols around moving people in quarantine, she said. People needed to be tested before they were moved and they could not be on flights with people outside of quarantine and isolation.

On the reports of the new case at the Auckland hotel, Ardern said: "I am going to leave Health to do the reporting of cases but when someone is moved then there's a protocol in place that means everyone stays exactly where they are when they are tested positive or symptomatic."

Yesterday the Ministry of Health reported two new cases in managed isolation facilities, bringing the total number of active cases in New Zealand to seven.

One of the two new cases was a toddler at the Jet Park Hotel in Auckland, and the second was a 59-year-old woman at the Grand Millennium.

Cook said being in full lockdown meant she couldn't leave her room for anything, whereas previously she was allowed into the foyer, and outside for exercise.

At this stage, Cook said she did not know when she would be allowed out of her room.

"The Defence Force did say that there would be an information flyer left outside people's rooms this evening to give us more information on what will be happening and what we need to do."

Another woman, who only wants to be known as TK, said she has been at the Novotel since Thursday night after flying from Australia.

She also received a phone call on Sunday evening saying a person staying there had tested positive and everyone would need to be tested tomorrow.

"All they have told us is to stay in our rooms as there has been a case of Covid."

She said she had seen a nurse each day to have her temperature taken but there hadn't been any testing since she landed on Thursday. This was despite the fact testing is meant to happen on days 3 and 12.

"We haven't been tested at all, now we are getting tested tomorrow because of this one coming up tonight."

The Ministry of Health would not comment, only saying there would be an update at Monday's briefing.

Both cases announced yesterday were recent arrivals from overseas and were detected within managed isolation facilities, the Ministry of Health said.

Neither involved community transmission.

The first was the young child of the couple announced yesterday as cases who have recently arrived from India.

"We are pleased to report that all family members are doing well at the Jet Park Hotel," the ministry said.

"We will not be providing exact details of the child's age but can say they are under 2 years old."

The 59-year-old woman travelled from Delhi and who arrived in Auckland on June 15 on flight AI1316.

She was tested at the Grand Millennium and was travelling with her partner, who has also been tested, and whose result is pending.

Active follow-up is now under way.

An update would be provided on Monday on this case and the follow-up of other cases from last week, the ministry said.

This couple are also now in quarantine at the Jet Park.

Everyone who was at the Grand Millennium while those people were there has or will be tested as part of the testing on days 3 and 12 that is now routine at all managed isolation facilities.

"This result was picked up in the woman's day 3 test and is an example of the new testing regime working as it should," the ministry said.

As of June 20, 36 children aged 0 to 9 in New Zealand had been infected with Covid-19. All have since recovered.

Seven cases of Covid-19 have been detected in returning passengers in the past week.