UPDATE 1-New Zealand authorities send extra fire planes to battle 1,100-hectare wildfire

New Zealand authorities said on Sunday that extra aircraft were being sent to fight an out-of-control wildfire that has burnt through around 1,100 hectares (4.2 square miles) of national park in the country's central North Island.

Firefighters began battling the fire in Tongariro National Park, a popular hiking spot, on Saturday afternoon and around 40 hikers had to be airlifted to safety. However, firefighting efforts were suspended overnight for safety reasons. Fire and Emergency New Zealand said on Sunday that more firefighting planes were being sent to the area, taking the number of aerial assets involved to eight helicopters and three planes.

"Because of the terrain and extent of the fire, air attack is more effective at this stage than bringing in additional ground crews across most of the fireground," Fire and Emergency New Zealand assistant commander Craig Gold said in a statement. Nine hikers were evacuated from the national park on Sunday morning, state-owned Radio New Zealand reported, citing a Department of Conservation spokesperson.

Fire and Emergency New Zealand said an aerial reconnaissance on Sunday would confirm the extent of the fire. Depending on what it showed, it was expected to take a full day of operations to bring the fire under control. The agency said it would have six fire trucks and five tankers on the ground battling the blaze.