Victorians flouting South Australia's COVID-19 border rules could face jail time with the state government moving to beef up penalties.
With two more border jumpers coming before court in Adelaide on Tuesday, the government introduced legislation to parliament to include a two-year jail term for offenders.
"As a government, we want to send the strongest possible message to those who break the law," Attorney-General Vickie Chapman said.
"We can't be too casual when it comes to protecting our state from the second wave of COVID-19 our Victorian neighbours are currently facing."
SA has a hard border closure in place with Victoria, preventing anyone except essential travellers from entering.
People arriving from NSW and the ACT must also quarantine for 14 days.
The tougher penalties come after four men stowed away on a train from Melbourne to Adelaide last week, and after three Victorians entered by road in the Riverland on Saturday.
Two more men were arrested after allegedly driving through a Dukes Highway checkpoint on Monday night by hiding their Mazda SUV between two trucks.
Police caught up with the 44-year-old driver and his 35-year-old passenger at Mt Barker, in the Adelaide Hills.
They were charged with failing to comply with a direction and were set to contest the allegations after appearing in Adelaide Magistrates Court.
None of those charged so far could face jail under the existing laws, which only allow for a maximum fine of $20,000.
Ms Chapman said South Australia had come too far to have reckless people enter the state illegally and unwind that good work.
"From the very beginning of this pandemic, we have always followed the advice of our health and law enforcement authorities, and this was no exception," she said.
"As soon as the police commissioner expressed his support for a term of imprisonment, we acted."
Police Commissioner Grant Stevens said while fines could act as a significant deterrent, prison terms should be an option.
He conceded, however, some people would still try to enter SA regardless of the consequences.
"That's why we've got so many police, supported by the defence force, on our borders trying to keep an eye on everybody coming across," he said.
Premier Steven Marshall has vowed to keep SA's hard border with Victoria in place for as long as necessary and said there would be no immediate change to the quarantine measures imposed on travellers from NSW and the ACT.
"There are many people who would benefit from this being lifted, but we cannot do it too early if it's going to be putting us backwards in SA," he said.
There were no new COVID-19 cases in South Australia on Tuesday, with the state's total so far remaining on 444.
SA has no active infections.