From midnight on Thursday, South Australians returning home from Greater Melbourne, Geelong and Bacchus Marsh must quarantine for 14 days upon arrival.

Returning residents from other parts of Victoria will not have to quarantine but must undergo tests on days one, five and 13.

Victoria is expected to enter a snap lockdown from midnight in an effort to contain the growing outbreak of the Delta variant.

"We don't want lockdowns in South Australia," Premier Steven Marshall told reporters.

"We are very concerned of the transmission which occurred at the MCG and so we need to take action to protect South Australia."

A 70km border bubble will remain in place.

About 150 South Australians must self-quarantine after attending exposure sites in Melbourne, the majority having been to the MCG.

The premier said there had been "a huge amount of movement" across the Victoria-SA border during the school holidays.

Border restrictions on southeast Queensland, including Brisbane, had been due to ease at midnight but will remain in place indefinitely.

NSW and the ACT also remain subject to tough border rules.

From midnight on Thursday, SA will return to stronger local restrictions including limiting private gatherings to 150 people.

Face masks must be worn indoors if venues are above 50 per cent density and at all times in high-risk settings including nursing homes.

Restrictions on dancing and singing will also return.

"We do all of these things to make sure that we don't have a lockdown in South Australia," Mr Marshall said.

"Too many people in South Australia believe that we've mastered the coronavirus ... we cannot be complacent."

SA has so far dodged a local outbreak of the virus after three exposure sites were identified, linked to infected removalists who came into the state from Sydney.

There are 238 people who have been ordered to isolate and get tested after being linked to the exposure sites at Tailem Bend, east of Adelaide.

There were just 25 QR code check-ins at the Tailem Bend sites during the time of concern compared to 76 credit card transactions.

Police Commissioner Grant Stevens said the low use of check-ins was hampering investigations into potential exposure risks.

"CCTV, credit card details, GPS information and other information sources can take days (to receive)," Mr Stevens said.

"I don't know how many times we can keep reinforcing this: QR coding is absolutely critical.

"We know it's a minor inconvenience but it's a small inconvenience at this point in time that can have substantial benefits in locking down an outbreak and preventing South Australia from going into a full lockdown."

All freight drivers crossing into SA must also show proof of a negative coronavirus test undertaken less than 48 hours earlier or alternatively get tested within 24 hours.

Australian Associated Press