Interesting.
I remember reading about this in early teenage. There was this book I had in the bookshelf that I was extremely scared of, but would read it because - adrenaline rush. Anyway of all the supernatural phenomenon described in book this was something I found most intriguing. How can a body burn leaving no ashes behind. If there was heat enough to evaporate the bones, why didn't the bedsheets catch fire? Ok say it was a chemical reaction and all organic stuff dissolved in air what about calcium. Even if it went into vapours there is good amount of calcium deposits found around the place where person burnt. Though back then there was no internet and I could not find any other source to know what is exactly left behind and what not. Now that you reminded me I may dig a bit. Though I still think the answer to this if it was ever recorded, probably lies in mind of the criminal. Someone who though how about I blame it on a supernatural phenomena. I might be wrong. I will go see what are actual recorded cases if any.

Thanks for sharing this.