A number of classified letters written by Italy's 20th century dictator, Benito Mussolini, to his mistress have disappeared from the nation's state archives.
The letters are believed to be very sensitive
The documents, dating from 1937, are part of 12-years' worth of correspondence between the fascist leader and Clara Petacci.
Also missing are parts of Petacci's diary, detailing her tempestuous relationship with the Duce.
The letters are believed to be so sensitive that even historians were not allowed access.
Under Italian law, the missing documents were to be declassified in 2007.
The disappearance of the documents was discovered in December by the new head of the archive Maurizio Fallace.
The national archive's 170 employees searched 100 kilometres of shelves but found no trace of the missing documents, he said.
Petacci and Mussolini's letters cover the period between 1933 and 1945, when they were captured and executed as they tried to flee to Switzerland at the end of World War II.
As well as the 600 letters originally stored, the archive also included 15 volumes of Petacci's diary.
Petacci's heirs tried to recover the documents in the 1950s, but Italy's Supreme Court ruled that they belonged to the state.
Under the country's privacy laws the documents can only be declassified after 70 years.