A bunch of morans also think a nuke was popped off, but forward off the cliff making us look like kooks. Occams Razor there is a much simpler logical explanation for what had happened.
The components for for and explosion were already on site, AN as oxidizer and grain dust as fuel. If it was a nuke there would be radiation detected and anyone close to the blast would be heavily dosed because of the burst occurring on the ground and spreading dust. But continue on with fantasy land instead of looking at the facts. The question should be who started the fire to get the AN to fume, what cause the first detonation to release grain, would only take about 150-200 tons to match up with AN, and what cause the 2nd high energy explosion which triggered the high energy blast wave.
I would provide the fuel to the oxidizer and it would only have to be around 10% of the mass of the AN. Not as good as fuel oil but same general idea, grain is loaded with carbs aka carbon chains.
Or call it a missile factory so you have pretest when you blow it up down the road.