Twenty-one New Zealanders visited Covid exposure sites while they travelled in Australia - and are all now isolating while they await confirmation of negative tests, says the Ministry of Health.

So far, 17 have had initial tests and returned negative results and the remaining four contacts are awaiting test results. Of the 21, three are isolating for 14 days and the remainder are isolating until they return a negative day five test, said the Ministry in its latest Covid update.

The Ministry said contact tracing had identified the 21 people who had been in locations of interest in Australia. They include 13 people in Brisbane, two in wider Queensland and six in Melbourne.

New Zealand public health officials said they were continuing to monitor the situation in Australia, particularly in NSW, Queensland and Victoria, where there had been a growing number of cases.

Travel with NSW was paused on June 22 and with Victoria on July 16, the ministry said.

Meanwhile, New Zealand has three new cases of Covid-19 in managed isolation facilities today - and no new community cases

One previously reported case has now recovered bringing the total number of active cases in New Zealand to 17.

Of the three new MIQ cases, one arrived from Serbia and Montenegro last Wednesday, one arrived from a yet to be determined location on Thursday and the other came from Eritrea on Friday.

The ministry said in a statement the fishing ship Playa Zahara is now secured at a quarantine berth at Lyttelton Port within an exclusion zone not accessible by the public.

Of the 18 crew, 13 were transferred to an MIQ facility in Christchurch.

The five other crew will remain on the ship and health checks would be conducted daily, the ministry said this afternoon.

They said plans were in place if any of crew became unwell and Customs would maintain a presence at the port while the Playa Zahara was berthed there.

Three crew members tested positive for the Delta variant with no links to previously confirmed cases in New Zealand or to the Viking Bay. That is in addition to the three reported on Friday who also had the Delta variant.

The remaining genome sequencing results were expected over the next few days, the ministry said.

The ministry said the two crew members who previously tested negative, tested negative again in Christchurch.

Meanwhile, Victoria's lockdown looks to be extended as more people in the community test positive.

Whether or not the state's fifth lockdown will be extended after tomorrow will be known within the next 24 hours, after 13 new community cases were identified today.

A total of 10 new cases in managed in isolation were confirmed in New Zealand in yesterday's Ministry of Health update.

Of those reported, three are crew members from the Viking Bay fishing vessel who have remained on the ship in quarantine on Queens Wharf in Wellington.