Have we even found any underground facilities? I recall one with some hallways and rooms, but I would assume thruout Iraq there would be more.
I ma sure that there are many underground shelters or weapons burial sites that we did not uncover yet. Iraq is the size of California, unless we get very lucky or get a tip from someone or find some documents, we will not know about where the WMD or Precursors for WMD were found.
Hiding enough WMD to kill 10,000,000 people takes one buried shipping container.