Helicopters are working steadily to bring a scrub fire near Arthur's Pass under control, before forecast strong winds this afternoon.
Five helicopters are fighting the one-square-kilometre fire, which began about 2am this morning on Mt Horrible.
Canterbury deputy rural fire officer Bruce James said the helicopters were working to douse the perimeter of the fire.
"They're predicting somewhere between 50km and 100km winds so we really want that perimeter secure before the big windy thing comes."
Bruce James said livestock were threatened by the fire, but farmers moved them away.
"Fire weather is worsening later today - it's going to get north-west and warmer - so we're aggressively fighting the fire now to pull that in."
Bruce James said the fire caused rocks to fall on State Highway 73, which forced the closure of Arthur's Pass earlier today.
The NZ Transport Agency said the road had reopened to one lane under stop/go control, between Bealey and Cass.
It recommended SH7 (the Lewis Pass) as an alternative route to the West Coast.