More than 60 books were taken from the Swedish library in the 1990s and early 2000s by a member of staff who sold them under an alias to collectors around the world, with some of them ending up at auction houses in America.
Anders Burius, an academic who worked in the National Library of Sweden's manuscript department, confessed to his crimes in 2004. After being released on police bail he slit his wrists and severed a gas line in his building, causing an explosion which damaged several nearby apartments and injured a dozen people.
On Wednesday several of the more than 60 manuscripts that went missing were scheduled to be handed back to Gunilla Herdenberg, Sweden's chief librarian, in a ceremony organized by the FBI (Federal Bureau of Investigation) at the offices of the US Attorney in Manhattan.
It is the third time that Herdenberg has been sent to the US to collect stolen works, with her most recent visit taking place in 2013.
The latest manuscripts being returned date back more than 400 years.
“We have inspected the books and have confirmed that they are ours,” Herdenberg told Swedish broadcaster SVT on Tuesday.
“Which books they are, I cannot go into at present, but they are from the 1600s and are invaluable and of great importance to Sweden's cultural heritage,” she said.
“It's fantastic that we've got back those books and we are very grateful for the work [the FBI] has done in the United States.”
Herdenberg added that she was praying for further discoveries in future.
“We hope of course that we will be able to get hold of all the [missing] books,” she said.
Since Burius' high profile crimes took place, security has been considerably stepped up at the National Library of Sweden.