Previously unknown artworks by masters including Marc Chagall, Otto Dix, Max Liebermann and Henri Matisse are among those found inside a flat in Munich.
Prosecutors said the issue of ownership was still to be clarified. The total value has been estimated at about €1billion (£846 million).
Other artists whose works were found include Pablo Picasso and Henri de Toulouse-Lautrec, as well as Canaletto and Gustave Courbet.
More top news
A British paleontologist has discovered a new species of dinosaur while studying fossils in a Canadian museum.
Sebastian Michaelis, one of a small group of tasters employed by Tetley, can grade a variety of tea in just 15 seconds.
The number of obese diabetics undergoing drastic weight loss surgery needs to triple to tackle a "major problem" facing the NHS, Nice warns.