When the war in Yugoslavia started in 1991, the Yugoslav army entered Jasenovac, the World War II-era concentration campin Croatia. At the time, Simo Brdar, a Bosnian Serb who formerly was assistant director of the Jasenovac museum, took the archives to his home in the Serbian-run portion of Bosnia and Herzegovina.

He kept the trunks with the documents in his home until September 1999, showing them occasionally to foreign news crews.

Two years ago, the Croatian weekly magazine Globus quoted Brdar as saying, "The collection is in my flat, and I am the watch dog."

The trunks contain 2,500 books, 10,000 pages of documents and more than 6,000 letters, photos and postcards, according to Rupic.

During World War II, an estimated tens of thousands of people were tortured and killed at Jasenovac, known as the "Auschwitz of the Balkans."

Unlike most camps, Jasenovac was run not by Germans but by local Croatian fascists. The great majority killed were Serbs, but victims also included Jews, Gypsies and anti-fascist Croats.

Croatia's Culture Ministry said that under an agreement with the U.S. Holocaust Memorial Museum, the material will be returned to Croatia by the end of October.