I had my barbeque catch on fire before, I threw flour on to put it out...guess that was a mistake, it made it worse. I sense spoke with a fireman about it (a shameless excuse to talk to one) anyway he said to use baking soda, flour is a combustible. I now keep a huge costco size container of baking soda around for when I barbeque.

It was pretty scary I had flames coming out the sides that were about a foot high