Covid-19 Response Minister Chris Hipkins has paused quarantine-free travel from New South Wales to New Zealand while the source of infection of the two cases announced in Sydney in the last two days is investigated.
Whole-genome sequencing has linked the case yesterday to a recent returnee who arrived in Australia from the United States. A household contact of yesterday's case has today returned a positive test.
An epidemiological link has yet to be determined between yesterday's case and the recent returnee.
Hipkins said while the new case announced today is not unexpected as a household contact of yesterday's case, officials have assessed that with several outstanding unknowns in the situation in Sydney it is safest to pause the quarantine-free travel from 11.59pm today. This will be under constant review.
Hipkins said health officials had been following the situation in Sydney closely.
A likely source had been identified in a managed isolation facility, he said.
But there didn't seem to be an "obvious link" indicating a chain of transmission.
"We do acknowledge this has the potential to disrupt people's travel."
Flights from NSW are paused from 11.59 tonight for 48 hours he said.
The pause could be extended if further information comes to light.
"This isn't a decision we take lightly."
He said officials needed more time.
The risk from travellers from NSW remained low, he said.
No other states were included in the pause at this time.
"What you will see with cases like this ... is before we move to a restriction is we will gather enough information to make an informed decision."
"Everything is based on the information you have at the time. There will always be cases that are right at the margin where you need you to gather more information ... we are erring on the side of caution."
There was the ability to extend the pause depending on the information that came to light over the next 48 hours, he said.
On NSW contact tracing, he said he had a lot of confidence in the system and that it was one of the strongest in Australia.
Earlier New Zealand health officials were in close contact with their Australian counterparts after a second positive case of Covid-19 in Sydney in the past 24 hours.
Chris Hipkins said then that decisions on what steps were needed were being discussed this afternoon.
"The advice that I had earlier today was that there could be a likely source of transmission, which again, required further investigation.
"We're in close contact with Australian health officials."
He said they were having conversations this afternoon about 2.30pm.
"We will then know a bit more about what the Australians know and obviously make decisions where we need to."
He noted the Northland case earlier this year where there was no lockdown.
"We're treating cases in Australia the same as we would here ... We are ready to move quickly if we need to."
Hipkins added that if there was a pause, it likely wouldn't take effect until tomorrow just because of the logistics of the flights timetable.
The latest developments come after New South Wales recorded its second case of Covid today, a day it was revealed a man in his 50s from Sydney's eastern suburbs had returned a positive result.
The new case, a woman in her 50s, is the man's household contact.
It's believed neither the man nor woman had recently travelled overseas, worked in a hotel quarantine, border or health role, or come into contact with someone who did.
NSW Premier Gladys Berejiklian said officials had managed to trace the source of the man's infection to a case acquired overseas but there are concerns about a missing link.
It matched a traveller who arrived from the United States and stayed at the Park Royal at Darling Harbour before being moved into a quarantine facility on April 28.
Prime Minister Jacinda Ardern said earlier today that preparing for "scenarios like these" was all part of having the bubble.
She said the traveller from the US was still in quarantine.
She added she was happy with how quickly New Zealand was informed of the NSW case and the level of engagement with NSW health officials.
"So far, that information sharing has been very good."
Hipkins said sometimes getting more information makes the decision - whatever it ends up being - more understandable.
"When you think about the lead times involved in [pausing flights], you want to make sure you're making decisions that are going to stick - rather than say you're going to pause travel and then a few hours later saying you don't need to anymore.
"The risk is still very low. That doesn't mean there's no risk."
The Ministry of Health said earlier today that New Zealand officials were in contact with their Australian counterparts following the confirmation of a positive case of Covid-19 in the community in Sydney.
A list of locations of interest had been released by New South Wales health and had been published on its website.
Those in Australia who were at a location of interest at the specified times were asked to follow New South Wales health advice regarding isolation and testing, and should not travel to New Zealand.
New Zealand health ministry officials had requested airlines communicate this message to anyone before flying to New Zealand from New South Wales.
Officials were scouring CCTV footage to find how the infected man crossed paths with the traveller.