Munitions dumps do explode of their own accord sometimes.
The Soviets had more problems than most in that regard - this isn't really surprising. Sure, it could have been terrorist action, but Soviet/Russian ammo depots don't need any help to go "BOOOOOOOOOOOM!"
Was a regular occurrence in the Cold War.
The Soviets always had these huge ammo dumps with untrained or barley conscript troops looking after them.
Used to look at aerial images of these huge dumps looking at all the hazards and mistakes made.
It was more of a surprise when they didn't go boom