A female mine worker who returned to Queensland’s Sunshine Coast and tested positive for the highly infectious Delta strain is among six positive COVID-19 cases stemming from a Northern Territory gold mine outbreak.

Northern Territory Health Minister Natasha Fyles confirmed the six infections from the 900 workers linked to the mine and more are expected.

“We’ve gone up to six cases,” she told ABC radio on Monday.

“It is moving quite quickly and that number is likely to rise today. We’ve said to Territorians to be prepared for that.”

A snap 48-hour lockdown started at 1pm on Sunday after workers left Newmont’s Granites Mine about 540km northwest of Alice Springs, where a Victorian man had earlier tested positive.

“Everyone at the mine site has gone into isolation and the mine started shut-down processes and contact tracing commenced,” Chief Minister Michael Gunner said.

Queensland chief health officer Dr Jeannette Young said on Monday 170 fly-in fly-out mine workers were notified.

One female returned a positive test to the Delta strain.

“She was only out in the community for one day. She was with her family and they started a road trip that immediately came back.

“We don’t know where this virus might next pop up,” Dr Young said.

In South Australia, almost 30 workers have gone into quarantine along with their families.

SA Health says 29 workers who came to SA have been contacted and placed in isolation.

“When I went home last night we had results from 11 of those people, they were all negative,” Chief Public Health Officer Nicola Spurrier told ABC radio on Monday.

“I haven’t had any bad news on my phone this morning.”

About 400 fly-in, fly-out workers travelled in recent days to Brisbane and 250 flew to Perth, with 244 remaining in the NT.

NT authorities moved fast to track down those people who stayed but were unable to make contact with about 20 until Sunday evening.

Ms Fyles labelled it a “big step forward” for the NT in its outbreak fight.

“The Northern Territory is certainly facing its first serious COVID threat since the pandemic,” she said.

“The 48-hour lockdown is about a short, sharp lockdown so that we can get on top of it and we did receive good news last night.”

NT authorities believe the cases are likely to involve the highly contagious Delta variant.

Chief Minister Michael Gunner on Sunday said one of the positive cases had travelled to NSW and was being managed by authorities there.

Two from the cohort are isolating at the mine in the Tanami Desert but have been evacuated to the Territory’s Centre for National Resilience at Howard Springs.

The fifth case was one of the mine worker’s close contacts who lives in Palmerston, south of Darwin. He tested positive to COVID-19 while in the Howard Springs centre.

It is unclear how the sixth case is linked to the cluster.

Meanwhile, Darwin, Palmerston and Litchfield local government areas, and Wagait and Belyuen Shires have entered a full lockdown for 48 hours, with anyone leaving their home required to wear a face mask.

Residents are only permitted to leave home for medical treatment, to obtain essential goods and services, for work considered essential, one hour of exercise a day or to provide care.

The lockdown ends at 1pm Tuesday.