[JasonC]

Indeed, much more likely. As for the cell connection, the obvious rationale is that they suspect somebody was listening. That is, they were moving missiles or whatever, and people involved in the shipment communicated by cell. The NKs then think, "ah, so the NSA must have heard them". Sounds like the NKs think it was well aimed covert ops. Doesn't mean it was, incidentally. Paranoids can think whatever they like - even when somebody is out to get them.

[Physicist]

Sounds like the NKs think it was well aimed covert ops.

Boy, would I like to believe that it was! But blowups happen. If we could do that, we could take out Dear Leader.

[Chad_the_Impaler]

NKoreans probably know as little as we do about the cause. They were moving missiles by train. It blows up. Why? The technicians probably weren't sending a detailed play by play back to Pyongyang at the time. The stuff about the train collision and the hanging wires is probably made up.