The Northern Territory is expecting more COVID-19 cases after an infected resident from a locked-down community snuck past police and fled to a nearby town.

The woman and four others walked from Binjari Aboriginal community, 330km south of Darwin, to a nearby caravan park where they called a taxi.

It took them about 10km to the town of Katherine, where the group spent 12 hours, before police found them at a gathering of 11 people on Wednesday morning.

“Unfortunately, someone has got out and we now have to do a fresh lot of tracing,” Chief Minister Michael Gunner told reporters.

“She was at large in Katherine and she was infectious.”

The woman did not know she had the virus and her absence was detected after authorities went to her home to inform her she’d tested positive.

She was among 11 new virus cases detected on Wednesday, along with four other people from the Binjari and two residents from the remote Aboriginal community of Robinson River, 1000km southeast of Darwin.

It brings the outbreak to 51 cases. The majority of those infected are Indigenous Territorians. Nine are aged under 12 years. Four people are in hospital, all Aboriginal.

Katherine, 320km south of Darwin, has been locked down since November 15.

Authorities say that is likely to continue into December due to the infected woman.

Binjari, 330km south of Darwin, and nearby Rockhole Aboriginal community remain under extreme lockdown orders.

About 300 residents are only allowed to leave their homes in an emergency or for medical treatment. Food and other supplies are being delivered with the help of the Australian Defence Force.

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

The 21-year-old lied on her border entry form before travelling from Cairns to Darwin after visiting Victoria, where she contracted the virus.

She infected a man in Darwin before the virus spread to Katherine, Robinson River and Binjari.

Police Commissioner Jamie Chalker said the the woman and the three other people who left Binjari are likely to be fined $5024 each.

“What it’s done is immediately impacted 12 lives, if not several thousand people who live in Katherine,” he said.

More police have been tasked with ensuring no one else leaves the locked-down community.

Positive cases linked to the woman are expected as contact tracing ramps up.

Mr Chalker said it was also likely to prolong the lockdown in the two communities.

“This has been a significant step backwards,” he said.