Investigative reporter Tim Shorrock has an update at Gulf Coast Reconstruction Watch on the unfolding scandal about why evacuation buses didn't show up until a week after Hurricane Katrina.

Let's remember how important this story is to the Katrina saga. The botched evacuation of hurricane survivors is one of Katrina's biggest tragedies, perhaps the ultimate symbol of the incompetence and neglect of the relief effort.

Following the storm, the nation looked on in horror as thousands of survivors at the New Orleans Convention Center and other central locations waited in vain for the buses to arrive. If the buses had arrived like they were supposed to, there wouldn't have been the tales of horror from the Convention Center, about survivors giving up on FEMA and walking miles with children through toxic water, and other stories we now associate with the Katrina tragedy.

The details of the failed evacuation are still emerging, but this much is clear: all roads lead back to Washington. As Tim Shorrock revealed in his Watch investigation last Friday, it was the federal FAA that contracted with Landstar Express America -- a Florida company with ties to Gov. Jeb Bush -- to deliver buses for evacuations.

But as Shorrock reports, FEMA didn't even know FAA had contracted with them, and neither agency provided oversight to "verify that the services had been performed."

Adding insult to injury, bus companies that DID try to provide vehicles to rescue storm survivors were either turned away, or haven't been compensated for their work -- while Landstar was given $32 million in overpayments.

So while many of the Katrina response failures are in dispute, the bus evacuation tragedy has a clear source: the federal agencies who failed to coordinate with each other and police the corporations given hundreds of millions of dollars worth of government contracts.

The Department of Transportation's first audit of the contract, released this week, reveals the $32 million overcharge but ignores the larger questions of the evacuation operation:

The DOT audit, conducted in October and November, sought to determine if the FAA's controls over the evacuation contract ensured "fair and reasonable prices" and that the government received the goods and services it paid for. But it "did not assess the policies, procedures, or systems used by the contractor," the DOT said.

By sidestepping those assessments, the DOT avoided making any conclusions about FEMA's botched evacuation of New Orleans. That evacuation was delayed for nearly a week by bureaucratic confusion and Landstar's inexplicable failure to ask subcontractors about the availability of evacuation buses until Aug. 30, 2005, 18 hours after the storm hit and a full two days after New Orleans Mayor Ray Nagin ordered the evacuation of the city, as previously reported by Reconstruction Watch.

Responsibility for the failed Katrina evacuation -- the source of much of the storm's suffering -- goes all the way to the top. And if the DOT audit is any sign, the federal agencies appear unwilling to ask themselves the tough questions.

Only a full, independent federal inquiry can deliver the answers the public deserves -- and hold the appropriate people accountable -- for this most devastating federal failure.