Initial blazes in the region were sparked by lightning during a storm on December 8, fought by Rural Fire Service (RFS), National Parks, and Forestry crews. In the past 24 hours, they have been joined by a team from the Australian Wildlife Conservancy, which has been working to re-introduce bilbies and some other highly endangered small creatures in the Pilliga Forest.

Narrabri Fire Control Centre public information officer Kate Carter said these conservation areas were in the north west of the forest and still a fair distance from the main fire grounds at present.

Ms Carter said the main fire of concern, the Duck Creek fire, where the burned area continues to increase, after rising to 29,516 hectares overnight.

However, crews now have "black edge" along most the fire ground.

"Duck Creek still has an un-burned pocket on the western side where crews are looking to strengthen containment lines and black out as much as they can so it does not prove problematic later," she said.

"There are still some active areas along the southern edge of the Duck Creek fire and crews are working on that with the help of heavy plant and aircraft.

"The main areas of concern are those which are still active."

Ms Carter said crews were working to ensure "hot spots" on the eastern side were fully put out before a storm is expected to roll in at about 3pm on December 14.

"Our concern is high winds arriving with a forecast afternoon storm, along with more dry lightning," she said.

Fire crews have the Berrygill fire, north west of Narrabri, under control, with patrols monitoring anything that could flare up.

Ms Carter said 133 personnel were currently spread across the fire grounds and Narrabri Airport, where 26 air crew personnel were refuelling aircraft as well as undertaking fire protection activities.

"We've been trying to use more water and where we can't trying to use gel in preference to retardant," Ms Carter said.

The NSW RFS fire danger ratings for the Northern Slopes and North Western region remain 'high' for December 14 and 15, expected to increase to 'extreme' on Saturday, December 16.