The Telegraph gives the few details available in English on reports that a Polish home contains 300 works of art—at least one listed as missing:

One is on the Polish register of looted art after it disappeared from a museum in Katowice during World War II, while another dates back to 1532. Just how the man came to possess the collection remains a mystery as he has been unable to communicate since suffering a series of strokes. He has been placed under formal investigation for handling stolen art.

Art hoard ‘worth millions of euros’ found in Polish bricklayer’s shed (Telegraph)