Mr Wishnowsky said there was no known risk to surrounding property.
Wellington fire communications shift manager Tim Rees said the fire was reported at 5.50am yesterday.
Fire crews from Martinborough, Featherston, Upper Hutt and Wellington, as well as rural fire parties, were sent to fight the blaze.
Control of the operation was handed over to the Rural Fire Authority later in the day.
"All Fire Service appliances have left. It's now in the hands of the Wairarapa Rural Fire Authority," Mr Rees said.
Rural crews from Tinui, Wainuioru, Upper Hutt and Wellington remained at the scene throughout yesterday.
"This is going to be quite a long duration. The fire is probably going to go well into the night and maybe into tomorrow," he said.
Conditions were windy. "The fire is quite fast moving", he said.
Mr Rees said it was too early to know what had started the blaze.
"No investigation has been carried out. There might be a reason for it but we don't know."
The fire follows a string of forest fires around Wairarapa recently.
Last month, firefighters battled a 5ha blaze in a roadside pine plantation on Whangaehu Valley Rd, near Masterton, and an 8ha forest fire on Ngahape Rd, rural Masterton.
Both those fires needed several helicopters with buckets and more than 30 firefighters before they could be contained and extinguished.
