There are five new cases of Covid-19 in recent returnees in MIQ and 21 cases detected at the border.

The Ministry of Health earlier today confirmed that a shipping vessel now headed for a port in Christchurch has been struck by Covid; with 16 out of 18 crew members infected.

Members of the crew were tested for the virus at Port Taranaki on Tuesday, after several people on board reported flu-like illnesses, the ministry said.

The vessel, named the Playa Zahara, is now on its way to Lyttelton Port. Authorities say they are working on arrangements for those on board once they arrive sometime tomorrow.

"This includes whether they quarantine aboard the ship or are transferred to a quarantine facility on shore," a statement said this morning.

"If any confirmed cases are to be transferred, that will also be done using standard [infection protection and control] protocol."

The boat had been at sea for three weeks prior to the reports of illness and no one from New Zealand had been on the ship during that time. The Ministry of Health said the public health risk was low.

Whole genome sequencing is also now underway, health authorities said.

The ship is the second Spanish-flagged fishing vessel to be dealing with a Covid outbreak in the past two weeks.

A total of 16 crew members from the Viking Bay have been transferred to an on-shore managed isolation facility in Wellington after 15 staff tested positive for the virus.

The 16th person is one of five crew members who were left on board the ship who tested negative for Covid but who has since become unwell. They were transferred to onshore quarantine facilities on Tuesday "out of an abundance of caution" and have returned a second negative test.

The four fishing crew who remained on board will be having their day 3 tests today.

Quarantine-free travel from Victoria remains in place with health officials continuing to monitor the situation as the number of cases grows.

The Ministry of Health advised New Zealanders in Victoria who have concerns about quarantine-free travel to organise flights home as soon as possible.

Quarantine-free travel from New South Wales remains paused and managed return flights from Sydney are in place.

All travellers on these flights will have to go into managed isolation for 14 days when they arrive in New Zealand. Because of this, travellers from NSW are not required to have a pre-departure test before flying.

Travellers who have been in NSW on or after 10.30pm on 26 June are not permitted to travel back to New Zealand from other parts of Australia. Travel histories will be checked at the airport before flying.

The five new cases in MIQ today were from Brazil, Fiji and the UK.