A blaze the size of three rugby fields was battled by 18 crews last night at the edge of the Ashly Forest in Canterbury.

Emergency services were called to battle the inferno at 7.10pm and 8 crews remained on scene overnight.

Southern fire communications shift manager Brent Dunn said some staff would remain overnight.

The fire was in a logging skid site on the southwest edge of the forest, and was about 300metres by 50m when the fire service first arrived at the scene.

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The cause was unknown and wind made it difficult to fight, Mr Dunn said.

"It was also unusual terrain, on the side of a hill.

"It's been a challenging day with the weather conditions creating havoc."

He said other fires in the South Island - moistly in Canterbury - were caused by power lines being blown down.

"We've had some calls come in about roofs coming off in the last half hour - so it's still blowing."