Covid-19 has been detected in two Christchurch wastewater samples but no new cases have been reported today.
A Ministry of Health spokesperson said the virus was detected in samples taken in the southern and eastern parts of the city.
One of the samples is likely the result of a known case living in the catchment area.
"Investigations are under way to establish any link to known cases for the second sample, including any recovered cases that have recently left MIQ," they said.
Further samples are being taken, with results expected later this week.
The four household contacts of the person who was reported as testing positive for Covid-19 in Tonga remain in isolation and have all returned an initial negative result, they said.
Two close contacts are in isolation with public health oversight in Christchurch and two are in isolation with public health oversight in Porirua.
The spokesperson said it is important that anyone, especially those in Christchurch with any symptoms, no matter how mild, gets tested.
Testing and vaccination sites are available across Canterbury today. Please see the Canterbury DHB website for site locations and hours.
It follows the announcement of a record-breaking 162 new community cases today.
Of the other new cases, 156 are in Auckland and five in Waikato.
The latest cases come ahead of Prime Minister Jacinda Ardern's 4pm press conference revealing Cabinet's alert level decisions for Auckland and Waikato. Both regions are in alert level 3.