RIVERTON, Wyo. (AP) — Officials say a house fire in Riverton that left a 71-year-old woman dead was caused by a cigarette she was smoking while on oxygen therapy.

A coroner determined Sandra Hovander died from smoke inhalation and thermal injuries due to a fire that was caused by her smoking while on oxygen.

Fire investigator Eric Siwik says the combination of the heat and oxygen started a flash fire, which spread to ordinary combustibles in the home.

Siwik says the home was the only structure affected by the Feb. 20 blaze. The kitchen sustained most of the damage, while there was heavy smoke and heat damage to the rest of the structure.