OXFORD, England (CNS) — A top Polish historian has questioned claims by German researchers that newly opened Vatican archives contain information damning the role played by Pope Pius XII during World War II.

“This team has the advantage of having been to these archives, and we must face the truth calmly if some major new discovery is made,” said Jan Zaryn, one of Poland’s foremost Church historians.

“But I’ve never personally encountered a situation in which 11 volumes of material, published over two decades, are suddenly countermanded by a single document, found after a few days’ research.”

Fr. Hubert Wolf, a professor at the University of Münster, Germany, said that, after an early March visit to the Vatican Apostolic Archives, his team had found proof that the Vatican knew of the Nazi mass killing of Jews but denied it to diplomats.

In a May 1 interview with Catholic News Service, Zaryn said diplomatic sources had long confirmed that the pope, with Allied governments, had learned of the Holocaust by late 1942, adding that St. Paul VI had agreed to publish wartime letters and documents from the archives early in order to “end the campaigns” against his predecessor.

“In his 1942 Christmas message, Pius XII condemned the mass murders; although he did this in his own language and didn’t mention Germans and Jews by name, the message was censored by the Third Reich, since it was obvious what the pope was referring to,” said Zaryn, a former senator and expert with Poland’s National Remembrance Institute.