Nine crew members on board the Marshall Islands-flagged container ship MS Mattina have the Delta variant of Covid-19.
The Ministry of Health said whole genome sequencing had shown the variant wasn't linked to any previously confirmed Covid-19 cases in New Zealand.
Fourteen of the vessel's 21 crew had tested positive for the virus, with the vessel docked in Bluff.
Three crew members had evidence of past infections, and a fourth result was under investigation because of a high CT value.
The last three had returned negative tests with plans in place for them to safely leave the ship and isolate from the rest of the crew members.