A search is under way for a man believed to have become separated from a group of people who arrived in Western Australia on an “unknown vessel”.

The West Australian Police Force said on Saturday evening it was searching for a man who was believed to have become separated from a group of people in the vicinity of Mitchell Plateau in the far northern reaches of the remote Kimberley region.

Police have been advised the man might have been a passenger on an unknown vessel carrying a group of people who landed in a remote area of the Kimberley District on Friday.

Police said the land search operation was in its preliminary stages and was taking place in an extremely remote area with challenging terrain.

It comes after a group of 39 people from Pakistan and Bangladesh were found at Beagle Bay, north of Broome, in February after they arrived in WA by boat.

The group was flown to an offshore detention centre on the Pacific island of Nauru.

—with AAP