The Vatican has announced that it has received a ransom request of €100,000 for the return of two stolen documents by Renaissance master Michelangelo, the Telegraph reports.

One of the stolen items is a priceless letter written and signed in Michelangelo’s own hand. It is extremely rare, as the artist usually dictated letters to assistants, and then signed them. The Italian newspaper Il Messaggero suggests that it might be the only preserved specimen of its kind (see Freshly Attributed Michelangelo Bronzes May Not Be Michelangelo’s After All).

The other stolen item is a document that bears Michelangelo’s signature.

The ransom request was sent to the Cardinal Angelo Comastri, in charge of St Peter’s Basilica, who refused it, according to the Vatican spokesman Father Federico Lombardi (see Man Protests Italian Government Atop the Dome of St. Peter’s at the Vatican).

Michelangelo contributed to the design of St Peter’s Basilica between 1546-64 (it wasn’t completed until 1626). But it is perhaps the iconic frescoes that he painted in the ceiling of the adjoining Sistine Chapel, between 1508 and 1512, that have captured the imagination of art historians and art lovers the most.

The theft was kept secret for nearly two decades

Michelangelo’s documents have been missing since 1997, when they were stolen from the Vatican archives. The Vatican never announced the theft publicly—it only became known when the ransom request was revealed last Sunday.

Father Lombardi confirmed that in 1997, a nun who worked in the Vatican archives had informed officials of the disappearance of the documents. He did not offer any explanation as to why the Vatican had decided to keep mum about it for almost twenty years.

Il Messaggero describes the person that sent the ransom request as a former Vatican employee: someone who had to “know very well the rooms adjacent to the basilica,” which are not accessible to the public, and who knew “how to move, and where to look”.

Father Lombardi reported that the theft and ransom request are now being investigated by Police.

The case has certain similarities with the disappearance of the Codex Calixtinus—a 12th century illustrated manuscript—from the Santiago de Compostela Cathedral in 2011. It 2012, it was revealed that it had been stolen by a former employee of the cathedral, a freelance electrician that had worked there for over 25 years (see Spanish Electrician Who Stole Priceless Manuscript and €2.4 Million from Santiago Cathedral Gets 10 Years).