South Australia will embark on a COVID-19 testing blitz, targeting anyone recently returned from Victoria as well as anybody with symptoms of the virus.
The move follows the hard closure of the border between the two states and comes amid growing concern over the spike in coronavirus cases in Melbourne.
Anyone who has been in Victoria over the past two weeks is being asked to get tested, regardless of whether they have symptoms or not.
The blitz will also apply to anybody returning to SA in the coming days who will be asked to take a coronavirus test within 24 hours and again on day 12.
They will be handed a mask when they cross the border, which they will be required to wear when in contact with other people, and they will also be required to self-quarantine for two weeks.
Chief Public Health Officer Nicola Spurrier says SA would only be able to weed out any potential COVID-19 cases if people continue to get tested.
"I want to see the testing numbers go up in South Australia," she said.
"Because of the threat from Victoria, the only way I can pick up if the disease is here is if everybody with respiratory symptoms gets tested."
Premier Steven Marshall said the spike in virus infections in Victoria was a "stark reminder of why we need to remain vigilant".
"It's a blunt reminder. We can't rest on our laurels," he said.
From Thursday, only people returning home from Victoria and essential travellers are allowed to cross into SA.
The new restrictions apply to everyone arriving by road or air, while people living in cross-border communities will be restricted to a 50km radius inside SA.
Extra police resources have been sent to the border and Australian Defence Force personnel have also been deployed to help.
They will also be stationed at Adelaide's police operations centre and in Mount Gambier.
Police Commissioner Grant Stevens said while there was no indication of people sneaking across the border, the number of crossing points was a "significant challenge" to police.
"With support of the Defence Force, we're hopeful we can manage our existing allocation at border checkpoints," he said.
"Because we have resources deployed at the Adelaide Airport and patrols increasing compliance checks, if there is a need to beef up the numbers in the southeast, we will do that."
South Australia reported no new virus cases on Thursday and no longer has any active infections.
Australian Associated Press