Dargaville police are investigating the cause of a fire on the Pouto Peninsula that burnt around 200 hectares of forest and is costing tens of thousands of dollars to fight, including $86,000 on helicopters alone.
Detective Sergeant Jonathan Tier said the police are keen to hear from anyone who may have seen vehicle or people movement in the area prior to or during the fire, which started around 8.30am on Tuesday near Kellys Bay, about 50km southwest of Dargaville.
"We would like to hear about any activity, not just that considered to be suspicious," said Mr Tier.
Three helicopters and 80 ground crew battled for two days to control the fire, which by yesterday had burnt through 200ha, - consisting of 50ha of pine trees in a privately owned plantation and another 150ha of native scrub and wetland in the Punahaere Creek reserve, managed by the Department of Conservation.
There is a ring of burnt bush around the fire and the firefighting team have stopped it spreading.