UPDATED 8.05PM: Conditions are against firefighters working to control a large scrub fire in Canterbury's Craigieburn area.

The blaze is spanning 45 hectares, and has caused the closure of the road between Springfield and Arthur's Pass.

Department of Conservation rural fire spokesperson Andy Roberts says weeks without rain has left the landscape tinder dry and given the fire plenty of fuel.

He says the blaze could last several days.

Roberts says the fire is yet to be brought control, but inquiries have already begun into how it started.

"We've got an investigator on scene," he says.

"He's covered in soot and he'll be looking to try and find the ignition point."

Roberts says tinder dry conditions, and plenty of scrub has made life difficult for firefighters.