South Australian authorities are "watching closely" the COVID-19 outbreak in Sydney but remain confident contact tracing will identify the source of the infections.
With the cluster centred on Sydney's northern beaches growing to five cases, SA Police Commissioner Grant Stevens said it was a warning for communities not to become complacent.
"It's a stark reminder to everyone that even though we've effectively eliminated COVID-19 from within our communities, it can find it's way back in," Mr Stevens told reporters on Thursday.
"We need to be in a position to respond quickly if that does occur."
But the commissioner said it was very early days in respect to the outbreak and significant contact tracing would be underway.
"The effort that goes into contact tracing is immense," he said.
"We would anticipate that they would be able to identify the source of that particular infection.
"If that's not the case and we see a continuing spread of COVID-19 in the NSW community then we will reassess our border arrangements."
No new virus cases were reported in SA on Thursday, with the state now just six days away from declaring its recent Parafield cluster of infections officially over.
Authorities consider two incubation cycles, or 28 days, the necessary timeframe before an outbreak can be declared officially eliminated.
December 23 has been identified as the day after that period ends for the cluster, which stands at 33 infections.
None of those cases are still considered active.
Chief Public Health Officer Nicola Spurrier said the cluster was "fairly unique" with a lot of information collected on all of those who became infected.
She said the last person went into isolation on the 24th of November.
"So if you count 28 days from there it ends up being around the 23rd of December which is when we can say it's closed," she told an online forum.
Meanwhile, SA has moved to scrap its COVID-19 border checkpoints and has dispensed with the need for travellers to check-in online before crossing into the state.
The decision was taken to ease pressures on police resources and reflected the low levels of coronavirus across Australia.
Under the border arrangements, between 350 and 550 police and protective service staff work on the border patrols on a daily basis, including at Adelaide Airport and the road checkpoints.
They will now return to their usual operational duties with the redeployment to be completed over the coming days.
