There is no fixed timeline. It depends how many diffrent Authorities are involved and how effective they work together to find the real cause despite the fact that the finding is not pleasant. One of the biggest problems is that those findings are usualy taken later to "activate" the lawyer to claim back the losses. Now go and find out who want´s to take the blame.
A partially or early version of such a incident can be found shortly in such a process, two weeks later the direction should be found and then evaluated.
Final report, maybe under the Christmas tree in 2012....
Fly safe and land happy