Moving 400 tons of anything is a daunting task, be it bags of rice, or crates of C4. And doing it under the noses of surveillance planes during wartime and getting away with it, is nearly impossible. No, if there ever was anything in those storage areas, it was removed prior to the US entry into Iraq.
I agree, and I've been sold on the notion that it went via truck caravan to Syria while the UN security Council dithered about votes. [In fact I was just reminded that an article I found about the facility before the war had Uday (who I suspect might have been the family member who might have been in charged of the joint) quoted that September 11th would look mild compared to what they had in store for our troops. Didn't Uday and his brother travel to Syria (incognito) and then returned to meet their untimely and unsuspected fate? Going to try to find that article.]