WASHINGTON (AP) _ Sybil Milton, a leading American historian of the Holocaust who helped conduct a major review of Swiss World War II refugee policy, died Monday. She was 59.

The cause of death was not immediately known, said a spokeswoman for the Independent Commission of Experts on Switzerland in World War II.

Milton was vice chair of the commission, which last December issued a report that criticized Switzerland for closing its borders to Jews fleeing Nazi Germany just as it became known that Hitler was implementing his ``final solution'' that was to kill 6 million Jews, 100,000 Gypsies and others.

The country, a neutral state in the middle of Nazi- and fascist-controlled Europe during the war, admitted about 27,000 Jewish refugees, but rejected a similar number.

Milton was senior historian at the U.S. Holocaust Memorial Museum in Washington until 1997 and was curator of special exhibitions in the United States and Europe.

She was an adviser to German and Austrian memorials to Holocaust victims and was a member of the New York Academy of Sciences.

Milton taught at a number of universities including Stanford, Tulane, Columbia and Maryland and wrote books on Holocaust ideology, bureaucracy and art.