A school for adult learners in Adelaide is being closed, forcing about 70 students into hotel quarantine and requiring about 1100 other staff and students to self-isolate at home, amid fears over a growing cluster of COVID-19 cases.
SA Health says a student at the Thebarton Senior College, a woman in her 20s, has tested positive for the infection.
It follows confirmed infections in other students with the cluster now accounting for five of SA's nine active cases.
The students taken into supervised quarantine were regarded as close contacts, with the remaining students and staff regarded as casual contacts.
Chief Public Health Officer Nicola Spurrier said the action was being taken out of an abundance of caution and there was no suggestion of widespread community transmission of the disease.
"We are doing everything we can to keep this cluster under control," Professor Spurrier said.
"We are being extremely precautionary at this stage. We have not got community transmission in South Australia in any way, in a widespread form."
Health Minister Stephen Wade said the tactics being used had been effective in closing down previous clusters in South Australia, including one linked to overseas tourists in the Barossa Valley.
"These are important health steps to protect the community," he said.
The new COVID-19 case on Thursday came after none were reported in SA on Wednesday, and took the state's total number of infections since the start of the pandemic to 457.
The Education Department said details would be released on Friday as to how the students at the Thebarton college could continue with their courses.
With a record 6000 COVID-19 tests performed on Wednesday, Premier Stephen Marshall said it was clear South Australians had remained vigilant in the fight against the disease.
But his comments came as four more people were charged with breaching the state's coronavirus restrictions.
Among those was a 17-year-old boy who was arrested at Adelaide Airport on Wednesday after getting off a flight from NSW, via Victoria.
Police became involved because although he had government approval to fly home from NSW, he did not have approval to travel through Victoria.
"While police were clarifying his status, he allegedly became abusive and refused to comply with the direction to wear a mask," they said in a statement.
The boy, from Christies Beach in Adelaide's south, was charged with breaching COVID-19 directions and disorderly behaviour and sent to hotel quarantine for 14 days.
Australian Associated Press