The tragedy came just hours after a coroner had highlighted the importance of checking home smoke alarms regularly.
The body of the woman, who lived alone at Old Blarney Road, Cork, was discovered at about 1pm by a relative.
Superintendent Con Cadogan said preliminary inquiries indicated clothes near a heater may have caught fire, leading to the elderly lady being overcome by smoke.
Gardaí also discovered her two pet dogs and two cats dead at the scene.
Technical experts sealed off the house for forensic examination.
“We are fully satisfied that this was nothing more than a tragic accident,” the superintendent said.
The woman’s body was removed to Cork University Hospital where a postmortem will be carried out today.
Meanwhile, an inquest took place yesterday into the death, last August, of Ben Burke, 55, who died after a fire — thought to have been started by a cigarette — broke out in his bedroom at Roches Buildings, Blackpool in Cork city.
The inquest heard there was a smoke alarm near Mr Burke’s bedroom but it had no batteries.
“This emphasises the importance of checking smoke alarms and making sure there are batteries that are working. They should be checked at regular intervals because they do save lives,” said Cork City Coroner Dr Myra Cullinane.
Mr Burke, a father of three, lived alone in the terraced house and had last been seen drinking in a local pub.
Senior fire officer Adrian Spillett said fire fighters had to forcibly enter the house through the front door.
They found the fire had burnt through the ceiling of the hallway from the first floor. In the bedroom, on the first floor, they found a man lying dead on the bed.
Assistant fire officer Seamus Coughlan told the inquest there was an ashtray on the ground beside the bed and it was his opinion the fire had been started by “smoker’s materials”.
Garda James O’Sullivan said he found nothing suspicious in relation to the starting of the fire.
The inquest heard Mr Burke had been born Brendan Power in Drogheda, but had changed his name to Ben Burke in 2002.
His body had to be identified by dental records due to the extent of his burn injuries.
Deputy State pathologist Dr Margaret Bolster found the cause of death to be acute carbon monoxide poisoning due to smoke inhalation.