Queensland has confirmed another local case of COVID-19, the third reported on Sunday.
A miner who returned from working in the Northern Territory has tested positive for the virus.
The miner transited through Brisbane Airport on Friday night before travelling to the Sunshine Coast.
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Officials say they had been in the community for around a day.
This case comes after two positive cases were confirmed earlier on Sunday, both linked to a case involving an infected flight attendant.
Contract tracing and genome sequencing are underway but there are serious concerns the miner may have the highly infectious Deltra strain of the virus.
Several other people who worked at the mine have tested positive in other parts of the country with officials contacting around 900 people.
About 400 of those are believed to have travelled back to Brisbane.
The positive cases from the mine have prompted a snap lockdown in Darwin and surrounding areas.
South Australia also shut its borders to Queensland, Northern Territory, Western Australia and the ACT.
Read more: Darwin to enter virus lockdown
An updated list of exposure sites will be added to the Queensland Health website.
The Premier announced on Sunday that some restrictions would be tightened despite only being eased on Friday.
Venues will revert back to the one person per two square metre rule from 6am on Monday, while household gatherings will be limited to 100 people.
Annastacia Palaszczuk also gave her strongest indication yet that border restrictions in Queensland could be extended at any moment, warning Queenslanders holidaying in New South Wales to seriously consider abandoning their holidays to return home.