Potato Explosion?!

Last night I decided to make my twice baked potatoes. So, I scrubbed my 2 regular Idaho baking potatoes and poked a fork in each one. I had the oven at 350 degrees and put them directly on the rack. Normally I would just do this in my little toaster oven, but I already had the oven heated as I was slow baking some ribs earlier. Oh, how I wish I had. It would have been a smaller area to clean. As they seemed to be happily baking away in the oven we heard a muffled boom. I thought, oh that's the oven heating, you know how it can occasionally make sounds? Then I heard it again and Rich said - what was that?? That's when I opened the oven and discovered that my potatoes had EXPLODED. What the hell? Has anyone ever had this happen? I really have no idea. Anyway, hilariously enough of the potato had remained in the skin so I was able to complete my twice baked- once exploded potatoes - I just had to bake them in a pan instead of their skins. 

What on earth caused this? Needless to say, I will stick with my toaster oven next time this mood strikes! Thankfully my sweet hubby graciously cleaned the oven for me today since even though it is supposed to be "self-cleaning" we've heard that KitchenAid is notorious for blowing up the heater when you use it - another What the hell?!