Two Renaissance paintings that have been on display for decades at Hearst Castle were returned Friday to the heirs of Jewish art dealers forced to flee Nazi Germany. The ceremony followed a two-year investigation by state parks officials into the artworks' origins. The paintings once belonged to Jakob and Rosa Oppenheimer, art dealers who in 1935 were forced to sell work in a liquidation auction of their Berlin gallery. At the time, Germany required Jewish citizens to report their assets to the government. The Oppenheimers had fled to France two years earlier and, with the help of relatives, managed the gallery from there until their work was confiscated. Jakob Oppenheimer died in France in 1941, and his wife died two years later at the Auschwitz concentration camp in Germany. Among those attending Friday's ceremony was Peter Bloch, 73, a grandson of the Oppenheimers who lives in Boynton Beach, Florida. He said he was surprised to learn that artwork belonging to his grandparents had been discovered in California. "It's with a lot of emotion when I think of what my parents and grandparents had to go through," he said. The 16th century, oil-on-canvas paintings include a portrait of a man with a book and a necklace of shells around his shoulders that may be the work of Venetian artist Giovanni Cariani. Another is a portrait of nobleman Alvise Vendramin that is attributed to the school of another Venetian master, Jacopo Tintoretto. Both were hung in the Italian style Doge Suite at Hearst Castle, where newspaper publisher William Randolph Hearst put his most famed visitors, including Winston Churchill and President Calvin Coolidge. A third painting, of Venus and Cupid attributed to the school of Venetian artist Paris Bordonen, will remain at Hearst Castle under an agreement with the Oppenheimer heirs. Bloch and another Oppenheimer grandchild, Inge Blackshear of Buenos Aires, Argentina, took possession of the two pieces on behalf of the heirs' estate during Friday's ceremony at the Leland Stanford Mansion in downtown Sacramento. Blackshear, 73, who moved to Argentina with her family when she was 5, thanked the "people of California" for returning the paintings. She said the heirs planned to sell both works and split the proceeds. "When we started in Argentina, I've never seen somebody work as hard as my mother. We had a very hard time," she said during Friday's ceremony. "With this, my grandchildren will be able to go to a very good school, and I am so happy and so thankful." Friday's ceremony marked the 25th settlement in the US involving repatriation of artwork taken from Jews by the Nazis, said Erik Ledbetter, director of international programs and ethics at the American Association of Museums in Washington, D.C. US museums began investigating the heritage of their collections after the fall of the Berlin Wall. Heirs of artwork stolen by the Nazis have been reunited with pieces that have been displayed at some the nation's most prestigious museums, including the Metropolitan Museum of Art in New York, the Art Institute of Chicago and The National Gallery of Art in Washington, D.C. "The Nazis had a morbid fascination with committing their crimes under the cover of legitimacy," Ledbetter said. "They had a twisted genius for inventing legal mechanisms which seemed to be legitimate but in fact were mechanisms of theft, and that's what happened to the Oppenheimers." The Oppenheimer paintings were spotted by the family's Paris-based attorney, who saw a 1976 pamphlet featuring artwork at the estate built by Hearst in San Simeon, along California's scenic central coast midway between San Francisco and Los Angeles. Hearst filled the 165-room castle with 25,000 pieces of art - a fraction of his collection spread among his six estates. The publishing tycoon often used professional art buyers. In 1935, they purchased the three paintings from the I.S. Goldschmidt Gallery in Berlin and likely were unaware of their origin, said Hoyt Fields, director of the Hearst Castle museum. "If he had found out, even after he purchased them, Mr. Hearst in all indications would have returned them," he said. The three paintings were deeded to the state by the Hearst Corp. in 1972, when the castle and its contents became part of the state park system. Museum officials were in the midst of reviewing the collection in 2007 when they were contacted by the Oppenheimer family's attorney about a possible claim. The attorney, Eva Sterzing, traveled from Paris to attend Friday's event. "Of course, a wrong cannot be fully righted when the victims have long since passed away," Gov. Arnold Schwarzenegger said during the ceremony. "This theft of Jewish property was an early stage of the Nazi plan and the beginning of far greater offenses against the innocent and against humanity." Photographic reproductions of the two returned paintings will be hung next week at Hearst Castle. Tour guides will be instructed to tell the story to the thousands who visit the landmark every year. "It will give people from around the world a chance to learn about the Holocaust, learn about the different forms of persecution the Jews of Europe were subjected to," said Ledbetter, of the museum association.