INQUIRIES are underway after fires broke out in the Royal National Park on Saturday night.

Emergency services were called to Bottle Forest Road at Heathcote about 7.20pm on Saturday after up to six small fires were spotted in bushland.

Police were assisted by the Dog Unit and police airwing, Polair, while Rural Fire Services crews worked to extinguish the fires.

A short time later, four youths were escorted from the area. They are not in police custody.

Until the cause is determined the fires will be treated as suspicious. Inquiries are continuing.

Meanwhile NSW Rural Fire Fighters from Bulli, Helensburgh, Otford have extinguished a bushfire at Maddens Plain. Crews will patrol the area overnight to assure the blaze does not reignite.