Arthur's Pass scrub fire started in separate spots, police say

Canterbury police are appealing for a person driving a tractor and two cyclists seen travelling along SH73 to come forward.

A scrub fire that spread across 330ha of the Southern Alps may have started in separate areas, police said yesterday as firefighters battled to bring the blaze under control.

Ten helicopters had been called in to fight the fire, which broke out around 2.30pm on Monday.

The fire now has an 8km front and has forced the closure of State Highway 73 - the main road between the West Coast of the South Island and Christchurch. Canterbury police are wanting to speak to two cyclists and a tractor driver seen in the region around the time the fire started.

"This fire appears to have started in four separate locations along the east-bound bank next to SH73 yesterday," said Detective Inspector Greg Murton.

A member of the public provided police with dash-cam footage that showed two cyclists close to where the fire was believed to have started.

The cyclists, along with the tractor driver, were regarded as key witnesses to the inquiry.

The Department of Conservation has taken over the fire-fighting efforts.

The wind, which fanned the fire on Monday, remained light yesterday and firefighters kept it from spreading any further.

However, DoC fire technical support officer Craig Alexander said it had still not been contained.

Chiefs are preparing to get ground crews mopping up its perimeter, he said.

But the conditions are difficult.

"It's steep, ugly conditions," he said. "One hectare scrub fires can be challenging, let alone scrub, beech forest, wilding pine, patch fields, where you are in and out, and the firefighter risk is quite high."

Crews have been brought in from the North Island, Otago and Southland to give their Canterbury comrades some respite.

Canterbury crews are also staying on call in the region, which is tinder dry and on high alert.