I'm not an explosives expert, but to my knowledge, you've got to types of things: flammable and explosive. Flammable things make the huge, cinematic fireball. Explosive makes the strong pressure wave and all that. Obviously the fireball will throw out some pressure from all the heat.
If you ever ignite oxygen and hydrogen you'll see the difference. Oxygen burns, hydrogen pops.
And wow, lucky that wasn't in the tunnel or whatever they're near.