Have you ever tried to burn sawdust? It doesn’t usually burn well at all.
It does not burn well, but make a pile too big and it will catch fire from composting and smolder for a very long time. This pile sounds like it is x1000 in comparison to the ones we see here in the U.S.
A fire in a pile of sawdust this size is inevitable.
Actually, take a shovel full of sawdust and toss it into the air over an open flame. It creates a pretty fun fireball an mushroom cloud... not that I have ever done anything this irresponsible.
And certainly not with “smoldering flames”!