In New South Wales in Australia this week there has been an inquest into non-fatal fires and a fatal fire due to use of wheat bags. All of the fires were started by wheat bags that had been heated in microwaves. Concern is that the wheat can dry out/change structure with repeated use contributing to fire risk. Currently there is no Australian Standard for wheat bags.
Wheat bags under scrutiny in house fire inquest
ABC News Australia
29th of April, 2013