I saw that post to Mark. Still, I prefer to rely on better sources than Wikipedia for historical information. There are actually books on the subject. I believe one by Luciano Canforra, dedicated exclusively to the library, makes a strong case that the bulk of the destruction happened in the course of the Muslim conquest. Wikipedia may be a good place to begin researching, but is certainly not be relied upon by serious historians.
Hungary's Orban: Refugees threaten Europe's Christian roots (Reuters)
from the article: Waqf Temple Mount excavation raises archaeologists' protests