At this point, it hardly matters if it is accidental detonation or not for the following reasons --
1. The explosive seized was meant to blow up somewhere causing widespread death and destruction.
2. There was an explosion of the same stuff in Delhi, killing ~14 and injuring ~30.
3. There is probably a sh*t ton of explosive still in the wild waiting to blow up.
4. Responsibility of attack claimed by PAFF (JeM).
Now, pertaining to 4, our stance immediately is - "They are lying" when, we know for a fact that this (1 - 3) was orchestrated by some JeM module here. So, them taking responsibility means, they take responsibility for everything, including the Delhi blast.
They have GoI by their proverbial ba**s this time. Such timid response by the state is unimaginable.
This guy is claiming it was ANFO which was stored. I am having a very hard time digesting this.