[Drammach]

The fates of the library and university are largely unknown. Parts of both might have been destroyed in Julius Caesar's war against Pompey. They might even have been leveled when the Arabs took over the city in 641, their locations lost to posterity.

I always thought the Library was burned down, destroyed by a roman soldier..
Here, the article says it's fate is "unknown"..

Is the destruction of the Library just legend?

[SAJ]

There is an excellent article on the libraRIES of Alexandria, as nearly as I can tell completely objective, no axe to grind.

http://www.bede.org.uk/library.htm