One of two firefighters, who suffered severe burns in a bushfire near Albany, is continuing to fight for her life in a Perth hospital.

The 45-year-old suffered burns to 60 per cent of her body when she was trapped in a truck which was engulfed in flames on Friday.

She remains in a critical condition in the burns unit at Royal Perth Hospital.

A 24-year-old firefighter, who suffered burns to 40 per cent of her body in the same incident, is in a stable condition and has been moved out of the intensive care unit.

They were injured while fighting a blaze near the Two Peoples Bay nature reserve, east of Albany, in Western Australia's Great Southern.

It is believed a wind change put them in the path of the blaze.

The Department of Environment and Conservation's Jim Sharp says the younger firefighter is making progress.

"I can say that I did have the opportunity of speaking to the younger officer, who is now in a stable condition," he said.

"I was able to speak to her and that was encouraging I guess, to me and to others, to at least converse with her."

Three other firefighters were also injured and received treatment at Albany Hospital.

Overwhelmed

Albany's Emergency Management Co-ordinator says the firefighters had all the available protective gear.

Brian Pickford says there was nothing that could have protected the two women.

"All firefighters are supplied [with] what we call PPE, which is protective clothing that is to a large degree fireproof," he said.

"Their tankers are also very heavily protected but sometimes the intensity of the heat can truly overcome the safety equipment we provide them."

Mr Pickford says the fire was too overwhelming.

"We had firefighters that were caught in what we call an overrun situation," he said.

"I can't explain too much because that particular part of the fire is under investigation but needless to say they were caught in an extreme and very hot fire area."

The Fire and Emergency Services Authority says several crews are still trying to extinguish the blaze which has burnt through an estimated 1,500 hectares of bushland.

FESA says while the fire has been controlled, crews are continuing to mop up the scene.

It says it is impossible to tell how long it will take to extinguish the blaze.

Investigation

The Premier Colin Barnett has offered his sympathies to the injured firefighters.

He says the cause and the response to the blaze will be investigated.

"It does remind all of us the dangers that firefighters face when they're out there protecting us and our homes," he said.

"The risk is always there; what happened this time was a sudden change of wind and they got caught in that fire so hopefully they will both survive but it's very serious injuries they've got."

Police have interviewed a number of people, including the owners of the property where the fire started, and are investigating if the blaze was deliberately lit.