An SOS sign spotted by a helicopter pilot flying over a remote and inaccessible part of northern Western Australia has sparked fears a person or group of people could be missing.

The sign was spotted by a helicopter pilot flying over Swift Bay, 120 kilometres west of the Kalumburu Aboriginal Community in the Kimberley.

Police were alerted and officers from the Kalumburu Police Station were flown to the area last Friday with the assistance of a helicopter charter company to conduct a ground search.

They were unable to find anyone, although they did uncover evidence of a campsite.

Senior Sergeant Peter Reeves said officers were trying to find out if there was someone in the area who might be in distress.

"We've done a ground search and aerial search of the area and there are indications that there may have been someone camped there at one point in time, but it's just not clear how long ago that was," he said.

"We're asking for anyone if they have any knowledge for the person who may have been in distress and may have made that sign, if they can contact us.

"Likewise, if they know of anyone who is in distress who may be out in that area, that we've got an idea of who and what we may be looking for."

Site accessible by helicopter

The site is hundreds of kilometres north of the Mitchell Plateau, which is a popular destination for campers and off-road enthusiasts.

Officers were only able to access the site with the help of helicopter charter companies.

Helispirit, which runs tours across the region, provided assistance.

In a statement to the ABC, the company confirmed it transported officers to the site and said two pilots from its base at Mitchell Plateau also helped to canvass the area.

"A thorough investigation was conducted, but no persons were found in the area," the statement said.

Investigations are continuing.