Many people who arrived on Sunday, before the new directions came into force, were told they would need to quarantine for 14 days or return to NSW.
But police have now clarified that position with an updated direction which indicates those who arrived before midnight do not need to go into isolation.
Police Commissioner Grant Stevens went on Adelaide radio on Monday to apologise for the errors.
“It’s a very unfortunate set of circumstances. We can only apologise to the people who were given the wrong information last night,” he told radio FiveAA.
“We’re still trying to find out where the breakdown in communication came about.
“It has affected people and we’re very sorry about that.”
Stevens said calls were being made to people who were given incorrect information to ensure they were aware of their responsibilities, which did include getting a coronavirus test.
The confusion on Sunday came as Sydney’s virus cluster grew to 70 cases and as hundreds of people rushed to beat the midnight deadline, only to be told that the situation might have changed.
The rush also prompted long lines for virus tests, with some forced to wait for hours.
Under SA’s new rules anyone who has been in Sydney’s northern beaches area will not be allowed to enter the state.
The Greater Sydney region, along with the Central Coast and the Wollongong areas have been declared high community transition zones.
People arriving in SA from those areas from Monday will need to quarantine in a suitable location for 14 days and get tested on day one, day five and day 12.
Announcing the changes on Sunday, Premier Steven Marshall said authorities were aware of the likely impact on Christmas travel plans.
“So we don’t take these decisions lightly,” he said.
“But in this instance, we believe that this is the best way that we can protect South Australia from any seeding into our state.”
Chief Health Officer Nicola Spurrier said people from other parts of NSW would still be able to enter SA without going into quarantine as long as they have not been in Sydney since December 10.
SA reported just three new virus cases on Sunday, all returned overseas travellers in hotel quarantine, and is now just three days away from declaring its recent Parafield cluster officially over.
Authorities consider two incubation cycles, or 28 days, the necessary time frame before an outbreak can be declared eliminated.
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