Firefighters worked into the night on Saturday to try to contain a large bush fire near Warkworth.
The blaze at Dome Forest started at about 4.30pm on Saturday and quickly spread to cover more than 65 hectares of rugged terrain.
Three helicopters with monsoon buckets were helping to put out the fire and crews were expected to be in the area overnight. Water tankers have been sent to the area from Auckland.
Waiwhiu and Wright roads were closed and police urged motorists on State Highway 1 driving through Dome Valley to be extremely cautious because smoke was billowing onto the road.
A Fire Service spokesperson said skeet shooters were seen firing into the area when the fire started but it was too soon to tell whether that was the cause.
The Fire Service said no homes were threatened though advised residents to leave if the smoke became too thick.