MADRID (AP) — A museum in northwest Spain returned two 15th-century paintings to Polish officials on Wednesday after it was determined that they had been looted by Nazi German forces during World War II.

The paintings “Mater Dolorosa” (Mother of Sorrows) and “Ecce Homo” were handed over to a delegation from Poland’s culture ministry. According to Spain's Museum of Pontevedra, the works were originally believed to be by Dieric Bouts, a Flemish master born in the Dutch town of Haarlem, but now they are attributed to a member of his school or group.

The museum said that in 2020 Polish officials made it aware that the works had been looted by Nazi forces. The museum quickly decided to send them back to Poland, but the completion of official permits for the transfer had delayed it until now.

Nazi forces stole the works from the Czartoryski collection in Gołuchów when the city was occupied by the German military in WWII, Polish officials said. They appeared in Madrid in 1973 and had been in the Pontevedra museum since 1994 when they were acquired among over 300 works purchased from a Spanish private collector.

Poland saw much of its cultural patrimony destroyed or looted during the country’s wartime occupation by Nazi Germany and the Soviet Union, and about 500,000 items remain missing.

The country has been making efforts to recover as much as possible. The Culture Ministry has a division for looted art that keeps a database of missing objects and scours foreign collections and auctions. When they locate a looted Polish painting, book or other object, they inform the law enforcement officials of that country.

AP writer Vanessa Gera in Warsaw contributed to this report.