You mean before it explodes? What I understood is that Ben asked for some explosives, DImitri hand his bag to ben and, then, Ben comes back with the same bag, he hand't touched the dynamites because he said he didn't need to used them finally. So it wasn't a new box of dynamite, it was the same bag that dimitry handed him.
I have a theory concerning Nik's route so, if you haven't played the game, don't keep reading *SPOILERS*
When the dynamite explodes inside the mines and hurt Dimitri, everything points to Ben, but I don't think the most obvious one here is the answer. It could be Sam but... My theory is that Dimitri is the one who sabotaged his own dynamite. Yes, he get's hurt, but he is a soldier, after all, I don't think he wouldn't getting a little bit hurt. After this, after what I could understand (I'm not an English speaker, sorry) a civil war is starting, and maybe this was his plan. After all, he is a soldier, so he must be very stratigic.
There is also a comment that Sam makes when he met Dimitri for the first time something like: "If Nik and Dimitri fight, I don't know wich one could win." Maybe a final fight between Nik and Dimitri, being Dimitri the bad guy? XD
