It is not known if she is symptomatic or the move was precautionary.

The toddler's case was announced earlier on Monday when Health Minister Natasha Fyles said the child had attended Katherine Hospital a day earlier.

"It was at that point she received a PCR test and that has come back positive," Ms Fyles told reporters at the time.

An NT government spokeswoman later said the girl had been transferred to The Centre for National Resilience quarantine facility with a household contact.

A press release has since been released saying the toddler had been moved to Darwin's main hospital.

Health workers have tested seven other household contacts.

They are also attempting to trace the group's movement in the Katherine community.

The girl is not a known contact for another case and more infections are expected.

The current outbreak currently stands at 61 cases.

Ms Fyles said the case was likely to be linked to persistent positive wastewater tests in Katherine, 320km south of Darwin.

A lockout in the town has been extended for 24 hours and is now scheduled to end at midday on Wednesday.

A lockdown in the nearby Binjari Aboriginal community is set to be eased to a lockout on Tuesday at midday after the latest round of tests returned negative results.

Meanwhile, two returned travellers have also tested positive for the virus.

A woman in her 60s arrived from London a week ago and tested positive while in quarantine at her home with one other person.

Both have been transferred to the Howard Springs quarantine facility, near Darwin.

The other case is a man in his 20s who arrived from Melbourne at the same time.

He was quarantined at home with a person who became infected with the virus and has now also been moved to the quarantine facility.

The travellers' cases are not considered to be a threat to the NT community.

Genomic testing to confirm what strain of the virus all the new cases are infected with is underway.

One case of the new Omicron variant was detected in a returned traveller from South Africa last week. The man in his 30s was quarantined at the Howard Springs facility.

Across the NT, 95 per cent of eligible people have had one vaccine dose and 89 per cent are fully vaccinated, according to NT Health.

Australian Associated Press