WILMINGTON, Del. (AP) — Federal authorities have recovered about 400 handwritten pages from the wartime diary of a key Nazi adviser to Adolf Hitler after a 17-year search for the documents, officials said Thursday.

Alfred Rosenberg played a significant role in the slaughter of millions of Jews and other non-Aryans considered inferior under the Third Reich. He was convicted of war crimes at the Nuremberg trials after World War II and executed in 1946.

Feds Recover Key Nazi Adviser Alfred Rosenbergs Wartime Diary

WILMINGTON, DE – JUNE 13: The ‘Rosenberg Diary’ pages are displayed after federal officials announced the seizure of the long-lost diary June 13, 2013 in Wilmington, Delaware. The diary, which was discovered in upstate New York, was kept by Adolf Hitler’s adviser Alfred Rosenberg, a Nazi party official, between 1936 and 1944. Credit: Getty Images

Officials from the Department of Homeland Security and the Justice Department joined officials from the U.S. Holocaust Memorial Museum for a news conference Thursday to outline how they found the documents, which cover the years 1936 to 1944.

Gerhard Weinberg, professor emeritus of history at the University of North Carolina and a leading historian on the Nazi era, said the diary could shed new light on Rosenberg’s role in administering the occupied eastern territories, and his relationships with other high-ranking Nazi officials.

Museum officials wrote in a Web posting Thursday that the documents provide valuable information, as Rosenberg helped orchestrate the looting of artwork and other valuables from Nazi-occupied territory during that the time.

“Its discovery will undoubtedly give scholars new insight into the politics of Nazi leaders and fulfills a museum commitment to uncover evidence from perpetrators of the Holocaust,” the posting said.

Researchers have yet to begin a thorough examination of Rosenberg’s diary. But Henry Mayer, a senior adviser on archives for the Holocaust museum, suggested that it will offer some “amazing new evidence” and that he believes some of the material will contradict written history.

Rosenberg, a Nazi ideologue and propagandist, was the author of “The Myth of the Twentieth Century,” a 1930 book espousing the superiority of Aryan culture over the Jewish race. He later led the Nazi Party’s foreign affairs department and rose through the party hierarchy to become Reich Minister for the Occupied Eastern Territories in 1941.

“It is very possible that, at least to some extent, there will be clues not just to Rosenberg’s total lack of brilliance, but there will, or well might be, interesting bits of information on conversations he had with other important figures in the government,” Weinberg said of the diary.

“It’s important that as soon as possible, somebody decipher the handwriting and publish, hopefully, an annotated edition of this material,” Weinberg said. “It is also possible that we will all be disappointed. There may turn out to be very little that we don’t know.”

Feds Recover Key Nazi Adviser Alfred Rosenbergs Wartime Diary

WILMINGTON, DE – JUNE 13: The ‘Rosenberg Diary’ pages are displayed after federal officials announced the seizure of the long-lost diary June 13, 2013 in Wilmington, Delaware. The diary, which was discovered in upstate New York, was kept by Adolf Hitler’s adviser Alfred Rosenberg, a Nazi party official, between 1936 and 1944. Credit: Getty Images

Feds Recover Key Nazi Adviser Alfred Rosenbergs Wartime Diary

WILMINGTON, DE – JUNE 13: The ‘Rosenberg Diary’ pages are displayed after federal officials announced the seizure of the long-lost diary June 13, 2013 in Wilmington, Delaware. The diary, which was discovered in upstate New York, was kept by Adolf Hitler’s adviser Alfred Rosenberg, a Nazi party official, between 1936 and 1944. Credit: Getty Images

Feds Recover Key Nazi Adviser Alfred Rosenbergs Wartime Diary

WILMINGTON, DE – JUNE 13: The ‘Rosenberg Diary’ pages are displayed after federal officials announced the seizure of the long-lost diary June 13, 2013 in Wilmington, Delaware. The diary, which was discovered in upstate New York, was kept by Adolf Hitler’s adviser Alfred Rosenberg, a Nazi party official, between 1936 and 1944. Credit: Getty Images

Feds Recover Key Nazi Adviser Alfred Rosenbergs Wartime Diary

Pages with Alfred Rosenberg’s hand writing are seen during a press conference after the announcement of the seizure of the long-lost ‘Rosenberg Diary’ in Wilmington, Delaware on June 13, 2013.  Credit: AFP/Getty Images

Feds Recover Key Nazi Adviser Alfred Rosenbergs Wartime Diary

In this Nov. 29, 1944, image provided by the U.S. District Court of the state of Delaware, a Nazi document is shown. Federal authorities say they have recovered hundreds of pages from the wartime diary of Alfred Rosenberg, a Nazi party official and key adviser to Adolf Hitler. The translation of the document: Dear Mr. Rosenberg! Gauleiter Koch informed me of his telegram to you of November 12, 1944 regarding the conclusion of the Reich Commissar Ukraine s shutting-down work, and the correspondence preceding this telegram. I would be thankful if you would also bring to my attention your reply to this telegram, Heil Hitler! The red Geheim! in Gothic script at the top means Secret! Credit: AP

Among early translated excerpts is a passage from 1941 in which Rosenberg wrote proudly of a conference marking “the first time in European history that 10 European nations were represented at an anti-Jewish conference with the clear program to remove this race from Europe. …”

Later that year, Rosenberg wrote of reports that Russian leader Josef Stalin had ordered the 400,000 Volga Germans “to be dragged away to Siberia, i.e. to have them murdered. …”

“Yesterday I had a proposal drafted for communication by broadcast to Russia, England and the USA that in case this mass murder is implemented, Germany will punish the Jews of Central Europe for this.”

Other translated excerpts involve the 1936 Olympic games, including Rosenberg’s assertions that Britons were “angry about the negroes from the USA as they squeeze out the English during the Olympic Games.”

Officials said his diary was smuggled into the United States after the war, most likely by Robert M.W. Kempner, a government lawyer during the Nuremberg trials. Kempner died in 1993, and museum officials later took possession of some of his extensive document collection. But the Rosenberg diary remained missing until recently.

“One of the enduring mysteries of the Second World War is what happened to the Rosenberg diary,” said John Morton, director of U.S. Immigrations and Custom Enforcement. “We have solved that mystery.”

Mayer said the search for the diary dates to 1996, when two of Kempner’s former legal secretaries approached a Holocaust museum official about Kempner’s collection of papers.

Over the next several years, museum officials assessed and took possession of several documents from Kempner’s collection, although some material they initially viewed in 1997 at Kempner’s Pennsylvania home were missing when they went to retrieve the papers.

Mayer said officials later learned that the two secretaries and “another gentleman from upstate New York” had taken the papers.

Officials later found the materials at a home in Lewiston, N.Y., with the help of a private investigator and former FBI agent.

Acting upon a warrant issued by a federal magistrate judge in Delaware, authorities seized the diary in April. Authorities repeatedly refused to say who had the diary.

“After a bit of negotiation, shall we say, we were allowed to remove this material,” Mayer said. He offered no other details.