Six Vietnamese asylum seekers who escaped from detention in Darwin remain on the run, but it's unclear if authorities suspect they're still in the Northern Territory.

The ABC understands two of the detainees are part of a group of six who escaped while being taken to a medical facility last week.

Four were found and are back in detention.

The other four missing detainees escaped from the Airport Lodge facility earlier this month.

The Immigration Department says police are involved in looking for the escapees, and it is a matter for police to confirm if the search has extended beyond the Territory.

Police say it is a matter for the Immigration Department to confirm.