It started on farmland and has spread to scrub on Department of Conservation land.
The fire is spreading in hot, dry and windy conditions and it's too dangerous to put ground crews in.
"We don't have it under control in any way," she said.
"Helicopters are just tackling it from the edges and it is still running."
Chesterfield said crews would continue to fight the fire until dusk, but would then have to postpone efforts until the morning due to safety reasons.
"Crews won't even come close to putting the fire out this evening, unless it were to burn itself out," she said.
She said ground crews would monitor the fire overnight, with controls beginning again first thing in the morning.
