Let's not jump the gun on the chemical/agricultural site yet...both sarin and tabun have legitimate uses as pesticides. Plus, other pesticides are chemically similar to tabun and serin since they are organophosphates and can give false positives.
If the lewisite is confirmed, that would be pretty damning, as it has no other purpose than to kill people.
And to put the "cache" of BM-21 "medium range" missiles into perspective...well, that is a 122mm multiple rocket launch (MRL) system that is akin to artillery, which was developed by the Soviets in the '50s....on the low end of medium range (about 15-20 miles). The "cache" of 20 rounds would be half a standard 40 round rack (probably left over from the Iran-Iraq War...I wonder if it was found with a bunch of other conventional BM-21 racks). Does anyone know right off the size area that 20 rounds would create sufficient concentration of airborne sarin to be lethal? I heard an expert on Fox who said that for a chemical attack via artillery to be effective over a battlefield size area you have to fire hundreds of chemical rounds.
I'm glad we have found something...our credibility will be much worse if we don't.