The cause of the large grass fire near Millers Flat on Monday was "rock strike" as a farmer mowed grass for hay, Central Otago principal rural fire officer Owen Burgess said.
"Farmers need to be aware of the risk. I suggest they do it in the morning or late at night ... and suggest that they carry a fire extinguisher and/or some water so they can at least try to put out any fire".
Two helicopter crews, as well as the Millers Flat and Roxburgh volunteer brigades and Central Otago rural firefighters, were called to the fire in waist-high grass in paddocks by Smiths Rd, just before 5pm.
A spokesman said the blaze covered an area 1km by 500m at its peak.
