Socalled 'Spontaneous Human Combustion' is one of those urban myths that pop up here and then.
Of course there is not such a thing , because it is physically impossible . Nevertheless, the first such case had been reported + 'witnessed' , if I remeber rightly , in the late 19th century in Germany. It had ,at the time , been duly investigated by eminent scientists and found to be.... what else .... a hoax.