Bulahdelah and North Arm Cove Rural Fire Service personnel were called to the fire which started around 3.30pm.

Traffic was stopped by police for around two hours, and the highway closed as fire fighters extinguished the fire.

The cause of the fire is now being investigated by authorities.

“We know where the ignition point was and where it took off,” NSW Rural Fire Service inspector Cecil Miller said.

While they are not certain, inspectors believe a cigarette butt was the cause of the fire.

“People need to be vigilant with cigarettes and throwing rubbish out of their window,” Inspector Miller said.

During the afternoon there were reports of cars travelling on the wrong side of the road, before the road closure, to avoid the fire.

“If smoke is over the road you should stop and go back where it is safer; we advise people not to drive through smoke because you might be unable to see the white line and steer into the path of other traffic,” Inspector Miller said.

Controlled fires will be common over the coming weeks as property owners burn off before the start of the permit season.

“People are asked to burn off on their properties. They need to contact fire control and adjoining land owners, 24 hours before they burn,” Inspector Miller said.

Starting on October 1, a permit needs to be obtained from the rural fire service for all burning.

The predicted forecast over the summer will see dry days before periods of light rain helping the fire fighters.

“We are not expecting anything out of the ordinary,” Inspector Miller said.

To contact the NSW Rural Fire Brigade to register a burn off, phone 65555782 during office hours.