Two mariners who were in Auckland yesterday have tested positive for Covid-19 and are isolating on a boat off the coast of Taranaki.
The Ministry of Health (MOH) regards the public health risk as low, and has identified three contacts who are currently isolating.
Those three contacts include two people who work at the port and the driver who transported the mariners from Auckland to New Plymouth.
The mariners are part of a group of nine who arrived in Auckland on Monday before being transferred onto a deep sea fishing vessel in New Plymouth, the MOH says.
The seven other mariners have since returned negative Covid-19 tests.
All nine provided negative Covid-19 pre-departure test results before travelling to New Zealand.
After arrival in Aotearoa, the mariners were tested again at an airport testing site in Auckland prior to transfer to the vessel at Port Taranaki.
The Ministry says they were not in any public places during their journey. They arrived, were taken by "the national service provider" in a minibus to a testing site in Auckland, and then to the vessel. They stopped to use the toilets at a Hamilton isolation facility on the way to New Zealand.
Genome sequencing has been ordered to find out the variant.
"We are aware those involved in the transfer including the mariners followed good public health advice and wore PPE. Officials are currently determining exactly what those involved," a spokesperson said.
They believe it is a low risk situation.
A Ministry spokesperson says they entered into the country under an exemption so they did not have to quarantine.
"These mariners entered into New Zealand under an exemption contained within the maritime border order.
"It's important to note that all people such as mariners who this exemption applies to are still required to comply with full infection prevention controls."
MOH said the mariners came from a south-east Asian country.
The vessel has since left New Plymouth and is in international waters off the coast of Taranaki.
All nine mariners are onboard and isolating.
MOH is reviewing the flight and airport movements of the mariners as part of the contact tracing process.
There is "minimal additional risk to any of the contacts during the transfer process" due to precautions that were taken, the MOH says.