Wastewater testing in South Australia has picked up evidence of coronavirus at two treatment plants, as the state records a new case for the first time in 12 days.
A Victorian woman in her 20s who tried to travel through Adelaide Airport to Alice Springs without correct permission tested positive in hotel quarantine late on Friday.
She had arrived from Melbourne on a Jetstar flight on Thursday along with four of her cousins.
"We were not expecting this person to be coming into South Australia," Chief Public Health Officer Nicola Spurrier told reporters on Saturday.
"In fact, our normal procedure would have been to book a flight and send her back to Victoria but given she had four young people with her, we elected to put her in a medi-hotel."
The woman had no virus symptoms and further testing was being done to determine if it was an old infection, Professor Spurrier said, saying the woman likely had no close contacts.
Meanwhile, one of the positive sewerage tests came from a treatment plant at Bolivar, which has a catchment of 700,000 properties, including Adelaide's CBD where virus patients have been kept in hotels.
The other positive test came from Angaston in the Barossa Valley, covering about 2000 properties.
Prof Spurrier said the results did not necessarily point to community transmission and further wastewater testing will be carried in days to come.
"We can't trace that back and say there is definitely people in these areas with COVID-19," she said.
"It doesn't mean we have an infectious case out there but we certainly couldn't rule that out."
The virus was excreted in faeces for a "prolonged period" after someone tested positive, she said.
South Australia was cleared of active cases on Wednesday.
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