UPDATE: In the post I put up yesterday Plague Killing off Al-Qaeda Terrorists it appears that as I suspected it may have been a botched case of Al-Qaeda experimenting with unconventional weapons.
Though unconfirmed reports are now coming in stating that it is not plague, it only states that it was either biological or chemical in nature, but intelligence sources are unsure of the exact nature of the agent.
We will update this story further as information becomes available.