South Australia's bid to contain a worrying COVID-19 cluster has hit a snag with two new cases, a school closed and hundreds of more people forced into quarantine.
It's also put in doubt plans to ease coronavirus restrictions across the state next week after the outbreak forced a range of new measures to be imposed.
The so-called Parafield cluster now stands at 31 cases with about 4800 people in isolation.
Chief Public Health Officer Nicola Spurrier confirmed on Thursday that a Woodville High School student, who tested positive late on Wednesday, had become infected from a previously identified hotspot.
She said the teenager collected a takeaway order from the Woodville Pizza Bar on November 14, where a person known to be infected was working.
Professor Spurrier said a risk assessment would be done in relation to how infectious the girl was when she went to school on Monday, but all students, teachers and their families had been asked to isolate.
The school has also been closed until further notice and was being deep cleaned.
The second new case involved a man in his 40s, who was a close contact of an earlier case and was already in quarantine.
Professor Spurrier said while all people who went to the pizza bar had previously been asked to isolate, she was pleased the school student had come forward to get tested.
"I am strongly of the belief that nothing has been done that was wrong," she said.
"This exposure was way back at the beginning (of the cluster). We're still working through exactly this person's infectious period.
"We're trying to look at the interpretation of the data that we've got from her results and we still haven't nailed exactly how she got infected.
"Also, possibly, there might have been someone else who's had this infection that she might have got infected through... the jury's still out on that at the moment."
Despite making the link to the cluster, Professor Spurrier said the girl's case remained "concerning".
The new infections have raised questions over SA's plan to lift the virus restrictions imposed because of the cluster as early as next week.
Police Commissioner Grant Stevens said a meeting of the state's transition committee on Friday would consider making changes in the context of the latest developments.
"We'll take the advice of SA Health, but I think it's been made pretty clear we're still aiming for a Christmas that is as normal as possible based on the restrictions we had in place back in mid-November," he said.
"But we do rely on expert health advice, it's been very good for us so far in terms of managing the virus."
SA remains on track to lift its remaining border restrictions with Victoria from December 1, and will also roll out QR codes at the same time to allow people to check-in at stores and restaurants to enhance contact tracing.
"This is great news as we move to further open up our economy, creating and supporting jobs," Premier Steven Marshall said.
"The benefits of the COVID safe check-in means if someone tests positive, we can quickly contact others who may have been exposed to the virus."
Australian Associated Press