"Clearly there will be an investigation into what has led to [the Margaret River] situation," Barnett said.
"I know there is a great deal of public interest and probably anger about how this fire started and we will get to the bottom of that but right now we have to deal with an urgent and dangerous situation."
Although largely under control by late yesterday, the outbreak continued to threaten homes as firefighters were given extra emergency powers.
"I won't say I am confident of a win here today," Environment Department incident controller Roger Armstrong told a meeting of residents.
"It is still in the lap of the gods."
Announcing wider powers to force residents from the fire zone, close roads and take other emergency measures, State Police Commissioner Karl O'Callaghan said he would be happy to over-compensate.
"If it follows the trajectory we are predicting, there will be dozens and dozens of houses in the fire's path and that makes it a very serious threat, including schools and the Margaret River Hospital," he told Radio 6PR.
Furious residents and local authorities have demanded answers from the Environment Department over the spread of a prescribed burn in the nearby Leeuwin-Naturaliste National Park.
A prescribed burn is a fire set by authorities under controlled conditions - including the rate of its progress - to reduce undergrowth and forest litter in a bid to lower the threat of out-of-control bushfires.
But critics of fire management plans across Australia have warned in the past that dangers exist because of political conflict between various fire, forest and other agencies and interest groups.
While prescribed burns are supported by most groups, including farmers and conservationists, critics have also complained of competition and turf wars between brigades, districts, and government agencies.
Barnett said last summer's disastrous Perth Hills fires, which destroyed more than 40 homes, had boosted the use of prescribed burning. "Prescribed burning is necessary to limit the risk to people and property, but in this case it has gone wrong," he said.
Yesterday afternoon concern grew as the Margaret River fire spread to new areas, forcing evacuation of parts of Prevelly, at the mouth of the Margaret River about 11km from the main resort town.
The Leeuwin-Naturaliste Park fire was first set by the Environment and Conservation Department in early September and had been successfully managed until embers were picked up by strong winds and flown across its boundaries. Residents of the area said they fled for their lives as flames raced towards them beneath a massive column of smoke.
"We were right in the line of the smoke when it was first coming and then it just came very quickly upon us," Prevelly resident Nola Gaebler told ABC radio.
"My partner was at home. He saw the smoke and then rang me and said it's moving very, very quickly and we had very little time to do much - pack a few things and get out."
A Kilcarnup local giving her name only as Nita said she ran as flames came within 300m of her home: "It was intense, it was scary and I don't know if our home is safe."
As the fire raged uncontrolled on Wednesday evening police escorted a convoy of local residents and tourists to safety, with about 200 gathering on the beach at Prevelly and another 140 at an evacuation centre in Margaret River.
Many vented their anger at a community meeting yesterday, with Orchid Ramble resident Lane Alver telling the ABC that authorities were fortunate most people were still too shocked to be angry.
