Some witnesses have said that parts of the wing came off and hit the tail. The flaps on an A300 are huge and are a possibility. This is starting to sound like a one in a million accident. The Bush Administration must have more info than we do because they reopened the airports fairly quickly, they didn't ground departing flights, and no other planes went down, which I would have expected if it was terrorism.
That fact is far more reassuring than any blather from the NTSB. If the FAA grounds all airliners with the CF-6 in the next few days, I think we can conclude that this was probably mechanical failure.