Dio Cassius, Roman History 42.38.2
Barnes, R. (2004) ‘Cloistered bookworms in the chicken-coop of the Muses: the ancient library of Alexandria’ in MacLeod, R. (ed.) The Library of Alexandria: Centre of Learning in the Ancient World, London and New York, I.B. Tauris, p. 71.
After this, many battles took place between them [i.e. the forces of Caesar and Cleopatra and of Ptolemy XIII] by day and night, and many parts were set on fire, so that among other places the docks and the grain warehouses were burnt, and also the books, which were, they say, very many and excellent.