SAN FRANCISCO (CBS SF) — San Francisco public library officials say they have tried just about everything they could think of to track down long overdue books.

At the start of the year, they even offered a six-week amnesty period for patrons to return long overdue books and settle up their fines. More than 10,000 patrons took advantage of the amnesty — returning 699,563 borrowed materials. Another $329,797 in penalties was forgiven.

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But currently, officials told the San Francisco Examiner, there are still 13,000 patrons who owe more than $100 in fines

So library officials are turning to the city’s official bill collectors — the Office of Treasurer and Tax Collector’s Bureau of Delinquent Revenue — to track down dead beat patrons.

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“This initiative is the latest in our efforts to remove barriers to access and to address our outstanding liability,” Cathy Delneo, the San Francisco Public Library’s chief of branches, told the Library Commission last week.

According to the Examiner, the library collected $445,590 in fines and fees during the last fiscal year.

The new collection process will allow for payment plans and a chance to negotiate a lower amount than owed, something librarian staff are not authorized to do.

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The Bureau of Delinquent Revenue will direct mail three notices and send three email notifications to library patrons seeking to collect over a period of time beginning in January.