The vegetation fires started around 4.30am on Sunday and covered about 270 hectares of land near Porters Pass.
DOC Operations Manager Kingsley said the area could take 40 to 50 years to recover from the burn.
Kingsley said invasive weeds in the area might grow back faster than native plant species, hampering or even preventing ecosystem recovery.
The DOC website stated the park is a habitat for bird species like kea and kārearea/native falcon, as well as indigenous insect life and unusual high alpine flora.
Fire Area Commander Colin Russell said any fire like this would cause environmental damage, and that ecosystems in the area may have been affected.
The fire was on the edge of the Department of Conservation Tussocklands Park in the area, and fire services were informed by DOC of sensitive areas to protect.
On Sunday, 10 helicopters with monsoon buckets were used to stop the fire from spreading, and on Monday about 50 firefighters were sent to extinguish hot spots where it could flare up again.
Russell said high humidity and low temperatures overnight helped to keep the blaze under control.
State Highway 73 was closed on Sunday after the fire started then crossed the road. It was reopened on Monday with one lane, with access restricted due to Fire and Emergency work on the blaze.
Russell said there was danger to public using the road with high numbers of skiers driving to Porters Ski Area.
He said there were also trampers in the hills on Sunday which were located by Fire and Emergency and made safe.
The cause of the fires was still under investigation by a Fire and Emergency team, said Russell.
Police said they were looking into a connection between the fires and an ATM robbery in Darfield on Sunday morning.