The discovery came just days after the Bathurst 1000 on Mount Panorama where spectator numbers were limited to just 4000 each day as part of a COVID-safe plan to allow the event to go ahead.

A free drive-through testing clinic will be open in the Cooke Hockey Complex car park from 10am-4pm today and tomorrow, and 10am-2pm on Saturday, with testing also available at Bathurst Health Service and Bathurst Respiratory Clinic at Ochre Health on the grounds of Charles Sturt University.

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No positive cases of the virus have yet been found on Bathurst but NSW Health issued a statement on Wednesday night saying increased testing was the only way to find new infections and to prevent further spread.

Health authorities have called on anyone who attended the Bathurst 1000 to get tested as soon as possible, as well as Bathurst residents with any symptoms that could signal COVID-19.

"The sample comprises wastewater from over the past weekend and could indicate a current or previous infection in someone who attended or worked at the Bathurst 1000 motor race, a visitor to Bathurst, or even a local resident," the statement from NSW Health said.

"Visitors to and residents of Bathurst must be aware of any symptoms of illness, and immediately isolate and get tested should even the mildest of symptoms appear that you think might just be a cold. Symptoms like a runny nose or scratchy throat, cough, tiredness, fever or other symptoms could be COVID-19.

"After testing, you must remain in isolation until a negative result is received.

"NSW Health is urgently undertaking investigations, which include reviewing lists of all those known to have had the virus who attended or worked at the race.

"The only way to find new cases and prevent further transmission is to increase testing."

There are more than 300 COVID-19 testing locations across NSW. To find your nearest clinic visit https://www.nsw.gov.au/covid-19/how-to-protect-yourself-and-others/clinics or contact your GP.

Sewage testing for molecular markers of SARS-CoV-2, the virus that causes COVID-19, started in July, adding another tool in the fight against the global pandemic.

There is no evidence COVID-19 is transmitted via wastewater systems.

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