A woman in her 40s and her primary-school-aged daughter who live with nine other people in Katherine, 320km south of Darwin, tested positive.

Another woman diagnosed with the virus is in her 20s and lives with six people in the same small pocket in the town's east.

The new cases were found after health workers launched a testing blitz in four streets, which are home to multiple Aboriginal families.

A health order mandated tests for any resident seeking to leave the area, with those who refused ordered into quarantine.

Once tested, residents were free to move about the community.

The targeted and legally enforceable rule came after days of positive wastewater results and infections in two infants and a teenage girl.

"We knew we had cases in that area, it's been bubbling away for some time," Health Minister Natasha Fyles said on Friday.

"Yes, we need to learn to live with the virus in our community but we also need to protect the most vulnerable".

Despite Katherine's vaccination rate surpassing 80 per cent double dosed, pockets remain where people have resisted the jab and dodged testing.

The new infections bring the current outbreak to 67 cases with more expected.

It started when an infected woman illegally entered the NT in late October.

The 21-year-old was fined for lying on her border entry form as the virus spread from Darwin to Katherine and three Aboriginal communities.

Police launched a fresh investigation into the border breach after an Aboriginal woman died from COVID-19 in early December.

Meanwhile, the fourth new case reported was a man in his 60s who tested positive after travelling to Darwin from London aboard a Qantas flight.

Two other household contacts linked to the flight have previously contracted the virus.

Across the NT, 92 per cent of people aged 16 and over are vaccinated, according to NT Health.

The Commonwealth data indicates it's closer to 80 per cent.

Australian Associated Press