Dozens of pages were ripped in the books. The libraries have counted 265 damaged books at 31 municipal libraries since the end of January. An official at one library said all the books could have been found using the keywords "Anne Frank" in an online database.
The motive is unclear. Police are investigating.
At least one library moved Anne Frank-related books behind the counter for protection.
Anne Frank wrote the diary while hiding from the Nazis. After her family was betrayed, she died in a concentration camp at age 15. Her diary has become the most widely read document to emerge from the Holocaust.
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