Bold catchers (for bolts set free at SRB separation) found to be operating
at safety factor of about 1.
Each bolt-half weighs about 40 pounds.

        http://www.msnbc.com/news/867336.asp?0dm=H12KT#BODY

It is believed that a bolt half may have fallen free from Columbia at SRB
separation but it is not believed to have struck the shuttle.

They are also recommending daylight only launches as part of any future
operations.

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