The 50 million pages stored in this central German spa town since the mid-1950s previously had been used by Red Cross staff to respond to inquiries about missing persons or the fate of family members, and later to document compensation claims.

The gray metal shelves and cabinets contain 16 miles (25 kilometers) of transport lists, camp registries, medical records, forced labor files and death certificates of some 17.5 million people subjected to Nazi persecutions.

Taken together with written and oral testimonies and the transcripts of war crimes trials, the dry data at Bad Arolsen add texture to the known picture of the Holocaust, from the first concentration camps created within weeks of Hitler's rise to power in January 1933 to the defeat of Nazism in May 1945.

"It was much more than I expected," said Trouve.

investigative researcher Randy Herschaft contributed to this article from Bad Arolsen