Although normally quite a few precautions are taken against it happening by the people handling the grain, assuming they're trained in it and know what they're doing as opposed to potentially being pressganged into it.
Of course if you know how to prevent it happening, you also know very well how to make it happen, and it may not take much for say one person who doesn't agree with what is going on to do something that either increases the chances of it happening "naturally" (disabling a safety feature), or actively working to make it happen (as I understand it it, a simple spark can be enough, let alone a naked flame).
I suspect it's more likely incompetence if it is grain, Russian sailors being tasked to load grain quite probably aren't among those who know to take precautions and/or are trained in handing it unless they happen to have served in a specific role in the merchant navy previously.
Shocking moment four Russian helicopters shot down in Ukraine (msn.com)
Hope this gets verified, nice result if true.
Blimey, that was quick work, nice one if correctly attributed!
