Two Italian art historians say they have discovered a trove of 100 previously unknown works by Renaissance master Caravaggio.
From a Milan castle, the paintings and sketches could be worth upwards of 700 million euros if found to be authentic.
Research was kept secret over the course of two years although the artworks have long been accessible.
On Friday, the historians published their findings in a two-volume, 600-page e-book in four languages.
The city of Milan owns the castle and officials remain cautious about the attribution.