Hi blada19t9,
It’s quite possible of course that it could be from some other factor (such as a treatment of the wood itself or even something to do with the conditions of the fire itself) but this is a question that I really can’t answer in specific terms. In the US … all foundations have to comply with the 1633 fire code (since 2007) and prior to this they had to comply with less stringent regulations (1632) but this is not the same in Canada. In many cases however … the products in Canada are manufactured the same way for manufacturing efficiency but there are may ways to comply with the fire codes in different countries and which one is used by any particular manufacturer or whether the specific product you have is fire resistant at all would probably be best asked of the manufacturer of the product.
You can read a bit more about this very complex and controversial subject in post #4 here along with post #2 here.
Phoenix