A mariner who is onboard a ship docked at Bluff has returned a weak positive Covid-19 test.
The Ministry of Health said in a statement today the man had been at sea for 25 days. He took a test in order to disembark to receive medical treatment.
Experts have assessed the level of risk to public health as being "negligible".
Further testing is being undertaken to confirm the infection is historical.
In addition to the mariner, there is one new coronavirus case in managed isolation today.
The new MIQ case landed in New Zealand on Saturday, May 15, having travelled from Indonesia, and tested positive on day one of routine testing in MIQ.
There is also one historical case identified in a recent returnee in managed isolation. That person arrived in Christchurch on May 9 from Japan and tested positive on day 3 of routine testing.
Authorities were also still awaiting test results from wastewater samples collected from Wellington, which are due this evening.
These new samples were collected following two earlier samples returning weak positive results.
Those results are likely due to recently recovered cases continuing to shed the virus, the Ministry of Health said.
The ministry encouraged anyone with Covid-like symptoms, especially those in the Wellington region, to get tested promptly.
Yesterday there were five new coronavirus cases in managed isolation and none in the community.
Those cases, who came from India, all tested positive within 0-1 days of arrival during routine testing. The cases flew into New Zealand at the end of last week.
With today's new case in managed isolation, the seven-day rolling average of cases detected at the border was one.
The country's total number of confirmed cases was now 2297.
Since the start of the year, there had been 61 historical cases, out of a total of 481 cases.
The total number of tests processed by laboratories to date was 2,085,298.
Laboratories processed 2727 tests yesterday. The seven-day rolling average was 3653.
Kiwis wanting to find their nearest testing location should visit the Healthpoint website.
The NZ Covid Tracer app now had 2,824,846 registered users. Poster scans had reached 270,147,364 and users had created 10,128,502 manual diary entries. There were 412,694 scans in the 24 hours to midday yesterday.