Ananova:

Librarians in the US have had to admit they are baffled by the case of the urine-stained library books.

Hundreds of books at two libraries, just 13 miles apart in Cleveland, have had to be thrown out.

Linda Yanko, manager of Geauga West Library, told the Plain Dealer: "I can't even believe we're discussing something like this. It's appalling and disgusting."

She said librarians had been finding new cases or urine-related vandalism about once a month with the recent case coming just this week.

The problems at Aurora Memorial Library began more than two years ago and damaged books have been found sporadically ever since.

Officials admit they have no idea who is responsible - or even if the incidents are related.