Wiki of the day: Spontaneous human combustion
An excerpt:
Spontaneous human combustion (SHC) is the alleged burning of a person's body without a readily apparent, identifiable external source of ignition. The combustion may result in simple burns and blisters to the skin, smoking, or a complete incineration of the body. The latter is the form most often 'recognized' as SHC. There is much speculation and controversy over SHC. It is not a proven natural occurrence, but many theories have attempted to explain SHC's existence and how it may occur.Link here