Note: I don't know what caused this latest explosion, but my general thoughts about Iran.
I will just lay down some basic hard facts, which maybe little unpleasant.
Iran (and also Russia) has shown time and again they have very porous internal security apparatus. Over past few years, I have seen countless such issues, from murder of scientists, killing of important personalities, bombings, terrorist attacks in both these countries. Nothing I have seen gives me the confidence that they have learnt anything from those incidents. It feels as if like there is no internal soul searching, they just carry on doing whatever they did earlier. If something bad happens in China, we see some concrete steps to rectify that. Every bad situation is studied and some sort of change happens. I think the thought process in both Iran/Russia is so regimental and archaic, they refuse to make changes or simply refuse to learn the hard lessons. When you are up against Israel/USA, you can't afford to be complacent and be so lackadaisical.