Hmm We (NATO) have white phospherous tiped munitions that also create these massive burns. All we have to do is target close enough, it incinerates the area. My bet is we're smuggling these munitions to the rebels by the hundreds. Assads crazy ass is cornered, he might try to say these burns are "chloride" based or mustered gas etc..just to be able to pull out his bio/chemical weapons.

Never swim too close to a drowning man..