You know, the reason I did not say any thing, in addition to the fact that the content of the container was unknown, was that I believe that standing right next to two hand grenades blowing up a 250 kg gas tank would instantly kill a normal human being. I inserted the "normal" to leave room for freaks of nature - just like us.
I know from the fire department in Oslo, that propane canisters of under 10 kilos have lifted buildings from their seating and torn verandas clean off of building faces. The shock wave is enormous. A diving tank filled with compressed air can shoot through a wall if the valve comes off. In the US they use aluminium tanks, and I've seen some photos of what can happen when they explode from wear - it's not pretty.
http://biobug.org/scuba/scubatank/