Rural Fire Service crews are battling to contain a fire burning out of control to the west of Mt Ousley Rd, Bulli Tops.RFS Illawarra Superintendent Andrew Pinfold said fire crews were alerted to about 1.45pm to the fire, which is burning in bushland in the Cataract Dam catchment area.The fire was about 10 hectares in size as of 3.45pm, but that figure had been revised down to 6 hectares by 5pm.There are no homes under threat from the fire.Six appliances, 30 personnel and a water-bombing helicopter have been deployed to the area and Supt Pinfold said crews were working to put containment strategies in place.Their job was being made more difficult by rugged terrain.He said it was too early to pinpoint the cause of the blaze, but investigators would work to determine the cause in coming days.