The shock announcement came just two days after the state government ordered people to stay at home and shut many businesses to combat what was considered a highly contagious outbreak of coronavirus.
South Australia state Premier Steven Marshall told a media conference in Adelaide that one man at a pizza bar tied to the outbreak told contact tracers he had only bought a pizza there, when he had actually worked several shifts at the food outlet alongside another worker who tested positive.
Authorities assumed the man, who wasn't named, had caught the virus during a very short exposure, leading them to believe the strain must be highly contagious.
"Their (the man's) story didn't add up. We pursued them. We now know that they lied," Marshall told reporters.
"To say I am fuming about the actions of this individual is an absolute understatement. The selfish actions of this individual have put our whole state in a very difficult situation."
While the outbreak was still worrying, Marshall said restrictions would be lifted early with a stay-at-home order ending at midnight on Saturday when most businesses would also be allowed to open.
Asked what punishment the individual might face, Police Commissioner Grant Stevens said there was "no penalty" for lying to tracers under the current law, though that would likely be reviewed.
"I think it is stating the obvious to say that this person's actions has had a devastating impact on our community," said Stevens. "The hardship is not lost on us."
Stevens would not be drawn on the man's likely motivation for misleading contact tracers.
Home to about 1.8 million people, South Australia has recorded 25 cases from the latest cluster, linked to a returned traveller from the UK. The number of new cases in the state was still expected to rise over the next few days.
The country as a whole has been relatively successful on containing the virus with only around 95 cases currently active.
The state of Victoria on Friday reported its 21st day of zero cases, a well-earned reward for a marathon lockdown of the country's second-largest city, Melbourne.
HOW DID THE INFECTIONS BEGIN IN SOUTH AUSTRALIA?
A security guard at a quarantine hotel, who also worked part-time at a pizza parlour, in the state capital of Adelaide, the Woodville Pizza Bar, was infected through a returned traveller from the UK.
A second worker, not identified by the authorities by name, at another quarantine hotel in the city also became infected. Authorities said the man told contact tracers that he had only purchased a pizza from the same bar, when in fact they later discovered he worked several shifts there.
Authorities worked on the premise that the man had contracted the virus from a very short exposure while buying pizza, leading them to believe he must have been exposed to a highly contagious strain.
WHAT ARE THE IMPLICATIONS?
"Had this person been truthful to the contact tracing teams, we would not have gone into a six-day lockdown," Marshall told a news conference in Adelaide on Friday.
A second consequence is that contact tracers now need to find and isolate a whole new group of people who have had contact with the man.
"There is an absolute need for us to move quickly over the next 24-36 hours to identify and locate these people so we know we have eliminated the risk of this particular strain spreading further into the community," Marshall added.
HOW DID AUTHORITIES FIND OUT?
The contact tracing team sat down and interviewed the worker. Another team reviewed the information obtained in the interview, but wasn't satisfied with "the feeling they got from this", South Australia Police Commissioner Grant Stevens said, speaking at the conference.
The review team went back to re-interview the man, who finally disclosed he worked several shifts at the pizza bar.
Premier Marshall said it was not yet clear what the man's motivation was.
ARE THERE ANY PENALTIES FOR THOSE MISLEADING CONTACT TRACERS?
No, though the current law would likely be reviewed.
"There is simply no mechanism for us to actually take any further action," Marshall said.
IS SOUTH AUSTRALIA OUT OF THE WOODS YET?
No. Authorities are still trying to locate thousands of people who may have had "dangerous contact" at the Woodville Pizza Bar.
The state's chief public health officer, Nicola Spurrier, also warned that the number of cases in South Australia would rise over the next couple of days, though those individuals are already in isolation and are not a threat to the wider community.
