Police are investigating the cause of a fire that killed Rose McArthur, 70, on Sunday night. They do not believe it is suspicious.

Her husband, Bob McArthur, was able to escape to the backyard where firefighters found him with non-life threatening injuries. He was taken to hospital "distressed and shocked" and suffering smoke inhalation.

ACT Fire and Rescue and police arrived at the McTaggart Crescent home about 7.45pm.

The cause of the fire is not yet known and police are investigating but ACT Policing Detective Inspector Matthew Reynolds said police did not believe there were any suspicious circumstances.

Neighbours said they heard an explosion, glass smash and people yelling just after 7.30pm.

It is understood a person driving by stopped and attempted to help the residents.

One neighbour tried to smash the front lounge room window, in an attempt to free those inside, but only thick, black smoke came pummeling out.

The neighbour, who wanted to remain anonymous, watched on as people did what they could to help before firefighters arrived, but the fire took hold too quickly.

"There was just this feeling of helplessness," she said.

"It was an inferno."

The fire quickly engulfed the front lounge room, she said, creating a ominous orange glow that spread into the street

The couple have lived at the Kambah address for more than 30 years. Neighbours Garry and Sandra Dodds said they were "like family", having lived a few houses down for decades as their children grew up together.

The couple were heartbroken by the loss of their friend, who they said was "the kindest person" and always willing to help anyone.

"She was an angel ... she had a heart of gold," Mr Dodds said.

Mrs Dodds will never forget watching Mr McArthur walking from his backyard as firefighters tackled the blaze that claimed his wife and destroyed his home.

"The look on his face of devastation will never go out of my head," she said.

Mr Dodds went straight to his friend as he emerged from the horror scene.

"He wasn't crying, it was like he was stunned," Mr Dodds said.

"He just looked at me and said 'Rose is gone'."

The former owners of RJ's, a takeaway food van in Woden had retired to their McTaggart Crescent home. Mr Dodds said Mrs McArthur had recently become unwell and more reliant on her husband for help.

"They were both dedicated, and they loved each other and you could tell," Mr Dodds said.

"It's just devastating."

The house was extensively damaged by the blaze and will be structurally assessed before it can be forensically examined. Police remained at the scene throughout Monday.

Detective Inspector Reynolds said a drone scoped the initial impact of the fire but it had not been determined where, or how, it began.

ACT Fire and Rescue superintendent Paul Flynn praised neighbours who tried their best to help free the residents.

"That is to be commended, however they were unable to enter the property due to the extent of the fire at that time," he said.

Police have called for anyone with dashcam footage or CCTV to come forward.

Superintendent Flynn said the incident was a tragic warning for Canberrans.

"Combustibles and sources of ignition within houses, we have to be careful of those, whether it's candles, heating, smoking," he said.

"We urge all Canberrans to keep gutters clean and just keep an eye on their property so it's not surrounded by combustibles."