BBC News | UK | New light on human torch mystery

Explanations include balls of lightning or a build up of methane inside the gut.

But forensic scientists are now convinced that the cause of such incidents is the so-called wick effect, started by a source as simple as a cigarette.

A pig was used because it closely resembles a human's fat content.

The pig was wrapped in a blanket and a small amount of petrol was poured on it.

After five hours of continuous burning the bones were being destroyed.

The wick effect means that a person could burn slowly without attracting attention from passers-by.

It also explains why only part of the body, the part which is rich in fat, burns while the rest stays intact.