Salt.
The WTC debris was shipped off to China before anyone could investigate. I don't believe they orchestrated it, but they were certainly complicit.
I concur with William Cooper's theory that several global interests–countries and secret societies–formed a temporary alliance after World War II to wage a depopulation/NWO agenda. This why you have Jews forming an alliance with China for decades and cabal interests moving American tech over there. But I remain unconvinced that China is running the show. More like they saw an opportunity and took it, and now they're one of the few left standing after the rest of that unholy alliance goes down in flames.