A lightning strike is believed to have caused a vegetation fire near Nelson last night.
A Fire Service spokesperson said crews were called to Sharland Creek, in the Matai Valley, where 50m by 200m of 10-year-old pine forest was ablaze at about 8.30pm.
He said it was too dark for ground crews to access the fire, so helicopters were used to douse the flames until late last night.
The fire is believed to have been caused by a lightning strike.
Firefighters will return to the scene this morning to ensure the fire has been extinguished.