Eddie that is one case of where they should have been allowed to carry on smoking ;O) Look at the cost it would save us keeping them in prison. All that would have been needed was a dustpan and brush to sweep up their ashes.
People at work (knowing that I am a caravan geek) asked why the cylinders did not explode. I suspect that our terrorist friends didn't bother to jam the valves so that gas was spewing out. Otherwise, I guess that it would take several minutes of intense heat for the things to actually explode.