Everyone who has recently arrived from Australia and are now in Taranaki should get tested for Covid-19, even if they don't have symptoms, the Ministry of Health says.
The ministry said today it could be due to recently recovered cases continuing to shed the virus or could signal undetected cases in the community.
In order to find out, anyone in Taranaki with symptoms or anyone who has visited Australia recently who has symptoms should get tested.
Extra testing capacity is now available in New Plymouth.
Find all testing stations in Taranaki here.
Microbiologist Siouxsie Wiles urged anyone in Taranaki with any hint of Covid-like symptoms to get tested.
"it's just a really important reminder that people, if they have any symptoms that could be Covid-19, go and get tested. They don't just think 'oh it's not in the community in New Zealand so I won't bother'."
Dr Wiles said an outbreak like that in Australia could happen here if transmission hasn't been detected.
Anyone with symptoms consistent with Covid-19 is advised to call Healthline on 0800 358 5453.
ESR tests wastewater throughout the country as part of an "additional surveillance tool", the ministry said. Further testing has been carried out and results are expected on Monday.
Mariners aboard the Playa Zahara and Viking Bay vessels recently docked at Port Taranaki, in New Plymouth, but the ministry said the the dates of their visits and the crew's activity did not appear to be a factor.
"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 ministry said in a statement.
All test results to date are negative with two results pending.
There are three new Covid-19 cases in managed isolation and two historical cases in New Zealand today.
The new cases come from the Philippines, Mexico and the UK.