The U.S. government asked a judge today to decide who owns a trove of Nazi documents that was taken from the home of a renowned war-crimes prosecutor after his death.

The papers, detailing Nazi dictator Adolf Hitler's plans to subjugate the Soviet Union, were kept for decades by Robert M.W. Kempner, a German who fled to the United States before the war and later prosecuted top Nazi officials in the Nuremberg trials.

Kempner bequeathed all documents in his possession to the United States Holocaust Memorial Museum, but tens of thousands of pages vanished from his suburban Philadelphia home after his death in 1993.

Some wound up in the possession of William Martin, who operated a business hired to clean and empty Kempner's home.

Martin gave the FBI the papers in 2001 when agents began investigating the incident as a possible theft. Charges were never filed.

Martin has since asked for the papers to be returned, claiming he is the rightful owner, according to a Justice Department lawsuit filed in Philadelphia. The Holocaust Memorial Museum also claims ownership of the documents, the suit said.

The Justice Department's suit asks that a judge decide the ownership of the papers but takes no position on who should get them. The files are sitting in an FBI evidence vault.

Martin did not immediately return a message left at his home. Holocaust Memorial Museum spokesman Andrew Hollinger declined to comment on the suit.