New Zealand health officials are in close contact with their Australian counterparts after a second positive case of Covid-19 in Sydney in the past 24 hours.

Covid-19 Response Minister Chris Hipkins said 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 today 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 has 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.

- words by Derek Cheng, NZ Herald