An image of the fire earlier today taken from inside a blocked off part of SH73. Photo: Supplied Darryl McCabe via RNZ
Six helicopters were now battling the blaze at Porters Pass, about an hour west of Christchurch, that began at 4.30am on Sunday.
A spokesperson said the fire was covering about 100ha, with crews from Fire and Emergency and the Department of Conservation working to quell it.
A Fire and Emergency spokesperson said the fire is partly under control, and crews were close to controlling the remaining hot spots.
The spokesperson said the fire began in a gully about 4.30am, then burned through a part of State Highway 73, which remains closed between Springfield and Arthur's Pass.
No detour was available and people were advised to avoid the area.
The nearby Porters Ski Area has also been shut due to the highway closure.
