[quote]All fertilizer, organic and inorganic contains three primary macronutrients, nitrogen, phosphorus and potassium. These macronutrients mixed with a variety of added micronutrients and other macronutrients help plants develop and grow. However, too much of a concentration of these nutrients can lead to fertilizer burn, which can damage plants, lawns and gardens.[/quote] It's the stuff in that makes it explosive. So something or someone at the plant caused a reaction to make it go off. I was going to post a better quote, but because of the plant it was a sea of articles about it. So that's the best one I could find.