He has been called the Italian Schindler, credited with helping to save 5,000 Jews during the Holocaust. Giovanni Palatucci, a wartime police official, has been honored in Israel, in New York and in Italy, where squares and promenades have been named in his honor, and in the Vatican, where Pope John Paul II declared him a martyr, a step toward potential sainthood.

But at the United States Holocaust Memorial Museum in Washington, the tale of his heroic exploits is being removed from an exhibition after officials there learned of new evidence suggesting that, far from being a hero, he was an enthusiastic Nazi collaborator involved in the deportation of Jews to Auschwitz.

A letter sent this month to the museum’s director by the Centro Primo Levi at the Center for Jewish History in New York stated that a research panel of more than a dozen scholars who reviewed nearly 700 documents concluded that for six years, Palatucci was “a willing executor of the racial legislation and — after taking the oath to Mussolini’s Social Republic, collaborated with the Nazis.”...