BRISTOL, Ind. (AP): Authorities say a mobile home fire that killed a northern Indiana woman and her son was an accident, although the precise cause of the deadly blaze hasn't been determined.

Elkhart County Undersheriff Sean Holmes says an investigation concluded the fire was accidental, but did not establish what exactly caused the fire.

Holmes says there are several possible factors that could have started the Dec. 16 mobile home fire that killed 67-year-old Cindy Kabay and her 42-year-old son, Chad Russell.

Their bodies were found near the entrance of their home in Bristol, about 10 miles east of Elkhart.

The county coroner says Russell died of carbon monoxide poisoning, while his mother died of natural causes related to a long history of health problems.