On April 8, staffers at the Boston Public Library noticed that Albrecht Dürer’s Adam and Eve—an engraving valued at over $600,000—was missing from its collection. After an internal search, a Rembrandt etching was found missing as well. A month on, no one knows what became of the art—but police believe the apparent heist may have been an inside job.

The Rembrandt—the self-portrait pictured above—is worth about $30,000. According to Boston Police Commissioner William Evans, the prints may have been missing for over a year. Police are investigating an unspecified number of library employees, the Boston Globe reported last week, and Susan Glover, the library’s keeper of special collections, has been placed on paid leave. While it’s “clear that the BPL may have been the victim of a crime,” library president Amy Ryan told the Globe, it’s also possible that the prints were simply misfiled.

According to police, additional works may also be missing. A security audit of the library excerpted by the Globe yesterday claims that it has no complete inventory of its own valuables, and that “Current estimates for holdings are [in most categories] guesses made many years ago that have been adjusted with newer guesses along the way.”

If the Dürer and Rembrandt were stolen, an inside job seems exceedingly likely. The works are kept in a storage room only accessible to certain employees; visitors who wish to see them must give a card with their personal information and cannot access the “reading room” where they are brought for display without the accompaniment of a librarian.

It isn’t the first time Boston has lost a Rembrandt: in 1990, robbers disguised as cops made off with $500 million worth of art including three works by the Dutch master from the Isabella Stewart Gardner Museum.

Image via Wikiart. h/t Hyperallergic. Contact the author at andy@gawker.com.