ABC News just reported an interview with California astronomers that they observed parts separating from the Shuttle as it passed over California.
Oh boy. This just keeps on getting more and more sad.
Were the California astronomers the ones at JPL (Jet Propulsion Lab) in Pasadena? One of my friends works there.
The interview was live on the air with Peter Jennings. Apparently the Shuttle was observed as it passed over the Owens Valley and parts were seen “flying off” of it as it passed overhead. The astronomer interviewed said this was very unusual, having observed Shuttle passovers before.
The discussion also concerned itself with heat resistant tiles observed falling off during the Shuttle launch. While some tiles do fall off periodically with launches, a point was made that in some areas of the underside of the Shuttle are more critical than others. The interview said there is a danger of a “zipper effect” that if some tiles fell off during launch (or even upon re-entry) in critcal areas of the Shuttle, a zipper effect may very well occur cause a massive loss of tiles.
Coupled with reports coming out that tire pressure readings (for the stowed landing gear) was “abnormal” are also being raised that it is possible that enough tiles came off near the landing gear to trigger an alarm, eventually leading to the catastrophic failure.
According to this report, the last voice communication was at 8.59 EST. Were they over Texas or California then? How long would it have taken to travel from California to Texas? 
Source: http://www.ovro.caltech.edu/
A live NASA press conference occurring now is providing abnormal sensor readings and other telementry data observed consistent with a California flyover time sequence, and what the California astronomers observed.