Federal Health Minister Greg Hunt has announced three extra cases of coronavirus have been identified within South Australia's Parafield cluster.
A spokesperson for South Australian Health Minister Stephen Wade confirmed the cases, saying they were in addition to one case announced by the Premier this morning.
The spokesman said it brought the total number of confirmed and suspected cases in the Parafield cluster to 23.
Hunt said all the new cases were among the same family and there were "no cases of community transmission in South Australia outside of that cluster".
"We have seen widespread testing and South Australians have done a great job in presenting for testing and we encourage them to continue to do so," he said.
Premier Steven Marshall told State Parliament this afternoon there were "in excess of 5300 tests conducted yesterday", which was a record for the state.
"We all know that the incubation period for this disease can be up to 14 days so we still do have an anxious wait to see what the true situation is in South Australia but there is more and more data coming in all the time," he said.
He said the virus was transferred to a cleaner at the Peppers Waymouth medi-hotel "via a surface" and that they believe she infected two security guards but none were symptomatic.
He said he did not believe there had been a breach of the state's hotel quarantine system, but SA Health would conduct a "fulsome" review once the threat of the Parafield cluster was over.
Authorities have been scrambling to contact trace and contain a Covid-19 cluster in Adelaide's northern suburbs, which prompted sweeping new restrictions across the state yesterday.
Earlier today the Premier urged anyone with even the mildest symptoms to get tested.
"Thousands of people were tested yesterday ... I'm very grateful for that," he said.
"They do not want a second wave here and they're prepared to do whatever it takes.
"Data is absolute king during these outbreaks [and] time is of the essence."
Restrictions may extend beyond initial fortnight
SA Chief Public Health Officer Nicola Spurrier said the new coronavirus restrictions - which include limits on gatherings in homes and licensed venues and a temporary ban on community sport - may continue beyond the initial two-week period if it becomes clear there has been major community transmission.
She said a "large number" of people were in quarantine or isolation across Adelaide.
Professor Spurrier asked South Australians to limit their interactions with other people to help contain the outbreak.
"I really want people to think about whether they need to go out and about for the next couple of days [and] for the next week," she said.
"It's very important for people to reduce the amount of travel.
"What we want people to do is monitor for symptoms ... even if it's just a sniffle. Don't go 'oh, it's hay fever' - go and get a test."
SA Health has released a list of dozens of locations across Adelaide where people could have become infected.
Authorities have urged people to get tested if they have developed symptoms after visiting those locations.
Meanwhile, most Australian states and territories have instituted quarantine or self-isolation orders for people travelling from SA, or for those who arrived from the state within the past seven days.
As of yesterday afternoon, Queensland, Victoria, Tasmania, the Northern Territory and Western Australia had announced specific measures for people arriving from SA.
New South Wales and the ACT will keep their borders open.