From the STS-107 SECOND DAILY REPORT on the NASA site (I think thats where I got it from):
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STS-107 SECOND DAILY REPORT
.. At approximately 81 seconds mission elapsed time (MET), a large light-colored piece of debris was seen to originate from an area near the ET/Orbiter forward attach bipod. The debris appeared to move outboard and then fall aft along the left side of the Orbiter fuselage, striking the leading edge of the left wing. The strike appears to have occurred on or relatively close to the wing glove near the Orbiter fuselage. After striking the left wing the debris broke into a spray of white-colored particles that fell aft along the underside of the Orbiter left wing.
..
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However, in all the news conferences the debris was said to have struck the underside of the wing.