I imagine that many New Orleans and Louisiana politicians made sure their own account books "happened" to be destroyed by the flood.
I think Blanco was afraid to let the Feds take over too soon, because, if she lost control, someone might have stumbled across some evidence which would incriminate her and/or her cronies. ...Incriminating Oil-for-Food records were found in Iraq after the US troops were there.
I also smell a rat in her behavior. Something has not been right from the get-go.