The two new cases of Covid-19 identified in the Auckland community last night are the South African variant which is more infectious.
Covid-19 Response Minister Chris Hipkins said preliminary genomic sequencing showed a link between them and the Northland case from the Pullman Hotel.
The two completed managed isolation in the same hotel and at about the same time as the Northland woman, but were on a different floor from her.
Hipkins wouldn't divulge which countries the two cases arrived from but said it was neither South Africa nor the UK.
Everyone who has been at the Pullman during January will now be tested.
Three people from the hotel have now tested positive more than a week after they completed managed isolation.
Hipkins told Morning Report no new returnees would be sent to the Pullman Hotel, its staff would now not be allowed to move between facilities, and the air-conditioning would be kept on to flush out the air in common spaces.
"Until we've figured out what's happened at the Pullman we won't put more people in there. We won't take people out of there. We've delayed the release of people who were due to be released. We're endeavouring to control that risk as much as we can."
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Hipkins said further test results today would confirm if the new cases were active, or remnants of an old one.
"We are proceeding with a great degree of caution. Close contacts have been identified and been asked to isolate and test."
The Health Ministry has also put out a list of places the pair have been to.
He said about three-quarters of the people staying at the Pullman about the same time as the positive cases have been tested. There were still about 20 people yet to be contacted.
"All have come back negative barring about four. One was a historic case, the other a false positive and then we've got these two we're dealing with at the moment."
He said there was no evidence of community transmission in order to call for restrictions on social gatherings.
Lockdown the 'last resort' - Auckland mayor
Auckland Mayor Phil Goff told Morning Report it would be "premature to go into lockdown now".
"It's the last resort. If we need to do it, we'd have to do it but nobody wants to do it and nobody sees that in being critical in the absence of evidence that there has been wider spread in the community by these cases."
He said health was important but so was ensuring the livelihood of people and businesses.
"Lockdown ... it is the last thing you turn to."
Goff hoped health authorities were prepared for a rise in tests but urged the public to only get tested if they were symptomatic or had been in the same locations as the positive cases.
"Don't get tested if you don't need to be tested."
He said Auckland was more vulnerable to an outbreak because its airport was where most international returnees arrived and also where there were the most number of manage isolation facilities.
"That's a burden we carry for the rest of the country."
The three positive cases from the Pullman Hotel suggested some "systemic failure" and there was a need to get to the bottom of it, he said.
While New Zealand had been largely able to contain the virus, "we are not failsafe", he said.
As for the upcoming long weekends of Auckland Anniversary and Waitangi Day, he said there was no word yet from public health authorities to stay home. "At this point it not deemed necessary."
National Party reacts
National Party Covid-19 Response spokesperson Chris Bishop said people mingling in isolation facilities had been a concern for a while, and more so now in light of the new variants entering the country.
"The whole point of MIQ is you're not meant to catch Covid in MIQ."
He said it was vital that MIQ facilities were not the reason for further infections.
It was concerning that some people who had been in the Pullman were not yet reached, he said. "That's a vector for transmission at the moment."
The next 48 to 72 hours were crucial to finding the extent of the cases, he said.