Firefighters and two helicopters are fighting a blaze at a forestry site near Blenheim.
Volunteer fire crews from Renwick were called shortly after 4am on Wednesday to the Northbank area in the Wairau Valley, about 12km west of Renwick.
The fire spread over a 40 by 50 metre logging skid site on a 40 degree slope, making conditions difficult for firefighters.
But the fire is now contained and the Fire Service says no properties or surrounding land are at risk.
It thinks the fire was caused by spontaneous combustion within the site.