Herbert Schauer was arrested earlier this month in Munich, website Napoli Today said on Tuesday.
The executive director of the Zisska&Schauer auction house is suspected of being involved in the theft of 600 volumes from the Girolamini library in 2012.
The Naples prosecutor said that Schauer took a leading role in the “systematic damage and illicit exploitation of book heritage at the state library,” Napoli Today reported.
But Zisska&Schauer has wholly rejected the accusations and in a statement the auctioneers said they were “deeply shocked” by the arrest.
“The accusations raised against him are preposterous, absurd and totally groundless,” the statement said.
Auction house staff say that they were offered over 400 books in private ownership in Italy through an intermediary last May. They were due to accept the consignment when German authorities announced they were to confiscate four of the books suspected of being linked to the Girolamini library thefts.
They said in a statement: “To be on the safe side Zisska&Schauer decided to withdraw the whole consignment from the auction, particularly as information and rumours were spreading that there had been losses of books from the Girolamini library in Naples. This suggested to us that there might be a connection with the consignment we had received from Italy.
“However, all the books in the consignment are still in Munich as no conclusive evidence has emerged to date that any of the books we received were in fact stolen from the Girolamini library.”
The auction house said Schauer was arrested on August 2 at his Munich apartment after Italy issued a European arrest warrant.
Their opposition is unlikely to deter Italian authorities, who have already sentenced the library's director to seven years in prison over thefts from Girolamini. Marino Massimo De Caro was also banned from public office for life.
Other public officials caught up in the cultural scandal have received prison sentences of up to five years and four months and bans from office.
The Girolamini library in Naples was founded in 1586 and boasts around 159,700 volumes and pamphlets, in addition to 10,000 rare and precious editions and other works.
The Munich auction house was set up in 1983 and Schauer took over as managing director in January 2007. His business partner has stepped into the role of managing director while the case continues.