A research program testing for coronavirus in Canberra's sewerage system has found no traces of COVID-19.
The findings support the belief there have been no instances of community transmission in the ACT that may have gone undetected.
Researchers at the Australian National University carried out daily samples of Canberra's wastewater throughout May to test for samples of coronavirus.
The month of testing Canberra's sewage coincided when ACT health officials had declared the territory had been free of any confirmed coronavirus cases.
Environmental epidemiologist Dr Aparna Lal said the testing allowed for other cases of coronavirus that may not have presented at testing clinics in the ACT to be detected.
"Health officials can only test so many patients, and the worry has always been that there were higher levels of community transmission in the community because people weren't getting tested," Dr Lal said.
"We're now at a crucial point with the easing of social distancing measures and kids going back to school, and we will continue to monitor the sewerage on a daily basis for the next couple of months for any public health response."
Researchers have tested one litre samples, provided by Icon Water, each day from the Lower Molonglo sewerage treatment plant, which covers most of urban Canberra.
The litre sample is then concentrated before it is subjected to genetic testing.
While the testing uncovered genetic material for a range of other viruses, no traces of COVID-19 were found in the sample.
"We spent time validating the method of testing, and it was using really quite advanced genetic testing techniques," Dr Lal said.
"In no way will this replace the method of testing at clinics or hospital reporting, but what it is doing is further supporting it."
The technique of testing for substances or genetic material in wastewater has been used for several years by the Australian Criminal Intelligence Commission to detect illegal drugs.
The ACT is not the only jurisdiction to carry out testing for coronavirus through the sewerage system.
Similar testing has been undertaken in Queensland by the CSIRO and the University of Queensland, while testing is also under way in Victoria.
"Suddenly, the ACT is not alone in this, and it's a well-established method of testing," Dr Lal said. "What's interesting about it, as we ease social distancing measures, is we can continue to monitor on a daily basis to further support what health officials are doing for their pandemic response."
Dr Lal said the testing was being further improved and being made more sensitive so more viruses can be detected from each sample.
"Not detecting it was a good outcome because we now know there's no undetected levels of community transmissions, and it's all due to the work of the Canberra community," Dr Lal said.