Chief Minister Michael Gunner on Saturday told reporters the mine worker tested positive on Friday, after arriving in the Territory on June 18.

The man was asymptomatic, and only discovered the infection when he was alerted to a potential hotel quarantine breach in Queensland through a message from interstate authorities.

The man had travelled from Bendigo via Brisbane, where he was ordered into a quarantine hotel on June 17.

He was in quarantine for a single day, but is believed to have caught the virus there.

The man, who is believed to have been unknowingly infectious from June 18, then travelled to the Granites Mine in central Australia, 540km northwest of Alice Springs.

His diagnosis has forced the mine to shut down and 754 workers to isolate on-site.

"We're fortunate with the design and the location of this mine site that, for all intents and purposes, we can turn it into a quarantine facility in and of itself," NT Police Commissioner Jamie Chalker said.

A further 900 people, who have since flown to Darwin, Alice Springs, Perth and Brisbane, have also been ordered to isolate at their homes.

Seventy close contacts have been identified, and will quarantine at the Howard Springs facility outside Darwin.

"We are confident, we know all the people who have moved in and out of the mine site," Mr Gunner said.

"While we've never had a case of community transmission in the Territory, we have constantly prepared for this situation."

"We'll do everything we can to test, trace and track this virus, will always do whatever it takes to keep you safe."

The strain of the man's infection is not yet known, Mr Gunner said, but health authorities are assuming it is the "worse case scenario" Delta strain.

He says of those 900 who have gone into isolation - 244 are in the Territory, with 33 in Alice Springs and 211 in Darwin.

Authorities are also unsure exactly how the man caught the virus.

Chief Health Officer Hugh Heggie said the incident was cause for significant concern - both in the territory and other states.

"I want to be very clear that we are at risk," he said.

There are also concerns the man's infection could see the virus spread to the territory's many remote communities.

Mr Gunner moved to reassure communities the risk was low, despite the site's proximity to two communities.

"This mine site is quite isolated and some distance from both of those remote communities. So, I'm absolutely confident right now."

Mr Chalker said anyone who had visited the mine site had been specifically warned not to travel to remote communities.

"There is no need for panic," he said.

"My understanding if there are any at all, it would be a very low number - certainly in single figures."

Australian Associated Press