A positive Covid-19 test result has been detected in New Plymouth wastewater, the Ministry of Health says.
"A follow-up sample, taken yesterday, returned a second positive result this evening," the ministry says.
"Based on previous incidences, it is most likely that the two positive wastewater results are due to recently recovered cases continuing to shed the virus."
Health officials are investigating whether any recovered cases who live in the New Plymouth area have recently left a managed isolation facility.
Additionally, it is also possible that other recently recovered cases from elsewhere in the country could have travelled to New Plymouth.
ESR considers a single recovered person shedding the virus may be detected in wastewater.
While the mariners aboard the Playa Zahara and Viking Bay vessels recently docked at Port Taranaki, in New Plymouth, the dates of their brief visits, and the activity of the crew, do not appear to be a factor in these wastewater detections.
"Additional testing is being carried out for a small number of port workers and nurses, who have been in possible contact with the mariners. The nurses have previously been tested for Covid-19 and returned negative test results," the Ministry says.
There are no managed isolation facilities in New Plymouth.
There were 19 new cases of Covid-19 reported in MIQ today and none in the community.
The 19 new cases are all mariners in isolation.
Last night, genome sequencing of the crew on the Mattina confirmed they have the Delta variant.
In total there are now 15 positive Covid cases on that ship. All crew who test positive will remain quarantined on-board.
Thre crew members, including the captain, have tested negative and were safely transported to on-shore facilities.
Today's numbers also include the 16 previously reported cases on the Playa Zahara because they have been deemed current cases.
On the Viking Bay, four crew members remain in quarantine on-board the boat in Welington while the other 16 are in an on-shore quarantine facility.
More test sites are being set up in New Plymouth to ensure those who wish to get a swab can do so.
"We are closely monitoring this situation and additional public health advice will be provided if, and when, required."