The two mariners are currently on board a vessel in the Tasman Sea and have been deemed "low risk to public health" by the Ministry of Health.

They arrived in Auckland as part of a group of nine on Monday, who all returned negative tests before heading to New Plymouth and boarded a deep sea fishing vessel.

All nine are onboard and isolating in international waters off the coast of Taranaki.

In a statement, the Ministry of Health listed no locations of interest, but it would review flight movements and undergo further contact tracing.

"Due to the standard infection prevention controls and other precautions taken there is minimal additional risk to any of the contacts during the transfer process," the statement read.

"Public health staff have identified three contacts who are currently isolating, including two people who work at the port and the driver who transported the mariners from Auckland to New Plymouth."

The mariners' port of origin is not yet known, but is not Australia.

Australian Associated Press