A MOTHER-OF-FIVE may have been killed by fumes from a burning Christmas tree.

Fire investigators believe Carol Churchill, 56, was overcome by toxic fumes from the plastic tree after it was set on fire by a cigarette.

The widow, who lived alone in Ellis Gardens, Hemlington, Middlesbrough, was found in the living room of her home by her brother-in-law on Tuesday afternoon - up to 36 hours after her death.

The fire, which caused 50 per cent damage to the decorated 6ft tree, failed to trigger a smoke alarm fitted in the end-of-terrace bungalow.

Middlesbrough station manager Andy Witham said an investigation carried out by experts from a forensic laboratory in Wetherby, West Yorkshire, had ruled out an electrical fire.

A post-mortem examination found Mrs Churchill had died of smoke inhalation and detectives investigating the case ruled out suspicious circumstances.

Mr Witham said: "It is a very unusual incident. The fire was well and truly out when we arrived at the house.

"We will never know exactly what happened, but somehow the lady's smoking material came into contact with the Christmas tree and started the fire.

"It was a slow-burning fire which didn't cause much damage, not even to the tree - but it could have been burning for a while.

"We can never be sure at this stage, but it would appear that Mrs Churchill's body could have been in the house for a considerable length of time - possibly between 12 and 36 hours."

One of Mrs Churchill's three dogs also died from the fumes.

"This should act as a warning to other people that they need to careful when they are smoking in the home," Mr Witham added.

"This was an unusual incident because even though smoke alarms were fitted they did not go off.

"However, we would recommend that alarms are always properly fitted and maintained."

The alarm was raised when the warden, who looks after the Ellis Gardens residents, failed to get a response from the house on Tuesday morning.

Detectives said Mrs Churchill rarely saw any of her five children, but she was in regular contact with her sister.

Acting Detective Inspector Paul Richardson, of Middlesbrough CID,

said: "Tuesday was the first time that the wardens had had cause to contact Mrs Churchill since New Year.

"There was no sign of forced entry and I am satisfied there are no suspicious circumstances surrounding this investigation."

A spokesman for the Royal Society for the Prevention of Accidents said the incident offered a reminder of the dangers of smoking.

He said: "This is obviously a very tragic accident, but it highlights the dangers of smoking in the house.

"While most deaths caused by smoking-related accidents occur in the bedroom, this is reminder of the dangers."

Cleveland Police said the investigation into the cause of the fire had been completed and a file would be submitted to the coroner's office.