Samples from Christchurch were collected on January 25 for testing and have all come back negative.
Meanwhile, samples taken in Whangārei on January 26 and from the North Shore, Western Auckland, Central Auckland, Hamilton and Rotorua on January 25 were also negative.
Two cases of Covid-19 were identified in Auckland last week after another was picked up a few days earlier in Northland. Testing around the area of the latest cases had not picked up signs of the virus, the institute said.
Dr Brent Gilpin says the negative results are pleasing but should not dissuade people from going for tests.
Earlier this year, testing of Christchurch's wastewater when there were a number of cases in managed isolation facilities, and sewage from the Jet Park Hotel, returned consistently positive results.
"Highly infectious individuals can shed billions of viruses, which means it is possible to detect in wastewater the presence of just a few infected individuals, but testing can't exclude the possibility of one or two infectious individuals," he said.
"It's an extra layer of protection to add to the existing methods New Zealand already has in place.
"Anyone who is symptomatic or thinks they may have been exposed to an infected person must get tested regardless of the sewage testing results."
Gilpin said the institute continued to collect and analyse sewage samples from other locations throughout the country.
It will report to the Ministry of Health any unexpected positive detections.
The wastewater surveillance research project is funded by Ministry of Business, Innovation and Employment.
