An outbreak of COVID-19 virus in Adelaide north has now been linked to 17 cases of the infection.
South Australia's Chief Public Health Officer Nicola Spurrier revealed the spike on Nov 16 after SA Health on Sunday found three new locally-acquired cases.
The new cases were picked up on Saturday after a woman in her 80s went to Adelaide's Lyell McEwin Hospital for testing and was hospitalised,
Two of her family members, a woman in her 50s and a man in his 60s, also tested positive.
One of the pair worked in a medi-hotel used by people travelling into the state and local residents who can't quarantine at home.
Spurrier said testing conducted overnight on Sunday included other members of the 80-year-old woman's extended family.
"We just kept getting positives coming off the machine," she told ABC radio on Monday, adding it was clear the cluster was linked to a medi-hotel.
"We haven't got the genomics yet, but I'm absolutely certain it has come from a medi-hotel," she said.
The 80-year-old woman lives independently and is the mother of one of the younger pair, who are in a relationship.
Contact tracing is also underway for about 90 staff and patients at the Lyell McEwin Hospital who may have come into contact with the older woman.
The woman had also visited Parafield Plaza Supermarket in Adelaide's north on Thursday while infectious.