Town and library officials first became suspicious of former library administrative assistant Linda Duffy in mid-July after questions arose about how overdue fees were handled, said Town Counsel John Vasapolli.”There were overdue fees that weren’t accounted for,” Vasapolli said Thursday. “There were questions about how certain funds were held and how they were accounted for.”That’s when Vasapolli said Town Manager Andrew Bisignani decided to launch an investigation, which was turned over to the Saugus Police and then the Federal Bureau of Investigation.Federal agents arrested Duffy on Wednesday for allegedly embezzling more than $800,000 in library fees and donations over a seven-year period while an employee there, according to her indictment. Duffy was put on administrative leave on July 22, and resigned six days later.Duffy appeared in federal court in Boston Wednesday, and was released on a $100,000 bond. The 65-year-old is charged with four counts of mail fraud, 10 counts of money laundering and one count of aggravated identity theft and is due back in court on Dec. 20.Bisignani said Library Director Diane Wallace had “concerns” shortly after she took over as director in June, and then came to see him.”I saw some evidence of wrongdoing and called the police,” said Bisignani. “There were indications of inappropriate behavior. (Wallace) was trying to get information that was not available and the answers she was getting from Linda Duffy were not suitable and raised a lot of questions so we dug a little deeper.”Bisignani said he thought the Library Board of Trustees should have caught the financial irregularities sooner.”The Board of Trustees should have had auditors looking at that and asked some questions,” said Bisignani. “It wasn’t a difficult thing to unearth.”Duffy had previously served time in prison in 1993 when she was charged with 13 counts of mail fraud, conspiracy and perjury. Duffy was sentenced to 21 months in prison after she used her position as a supervisor at an insurance company to write fake claim checks to her boyfriend totaling $120,000.Bisignani said he didn’t know about Duffy’s past arrest until these recent allegations first surfaced, and said criminal offender record information, or CORI checks, were not common when Duffy was hired in 1999.”We have them now, but back when she was hired it was the exception not the rule,” said Bisignani. “She was hired just as a receptionist and not to be in charge of funds. Her duties were very minor, I think she worked herself into a position of responsibility.”Bisignani said CORI checks are performed on all town employees now and said a CORI check would have kept Duffy from being hired.The majority of Duffy’s employment at the library was under former director Mary Rose Quinn, who stepped down in 2007 after eight years on the job. Quinn is now the director for the Stevens Memorial Library in North Andover and also serves on the Massachusetts Board of Library Commissioners.Multiple calls to Quinn’s office in North Andover were not returned Thursday.Since Duffy’s case is federal, Vasapolli said the town will wait and see how it is handled by the US attorney before taking any civil legal action.The US attorney is in charge of criminal possession and seizing rights, according to Vasapolli.”The federal statutes are much stronger when it comes to recovering the fruits of any crime,” said Vasapolli. “That would be a better route for the town to go. We’re victims, so any restitution would come back to the town.”On Thursday, Wallace said she’s hoping the allegations against Duffy won’t affect the library’s financial future.”I think we have a lot of loyal patrons and donors who are probably aware that the library does a good thing and we’re not just one person,” said Wallace. “But I’m sure people will be making careful considerations.”Matt Tempesta can be reached at [email protected]. You can follow him on Twitter @MattTempesta.