Capping years of tough negotiations, legal experts from 11 countries prepared treaty amendments Monday allowing the opening of Nazi archives that have been locked away from public scrutiny since World War II. Historians and Holocaust scholars say releasing the roughly 50 million files stored in the German town of Bad Arolsen would break the bottleneck in the search for Holocaust survivors or for the fate of the victims, and would open a mine of data about the Nazi death machine. The governing body of the International Tracing Service (ITS), an arm of the Red Cross body that oversees the archive, will vote Tuesday on changes in the 1955 treaty being prepared by a committee of lawyers and bureaucrats. It must be unanimous. If the changes are adopted by the International Commission for the ITS, the amendments will require ratification by the parliaments of some of the 11 nations on the commission. Until last month, Germany had blocked treaty amendments, arguing that access to the files by Holocaust researchers would violate German privacy laws. In April, German Justice Minister Brigitte Zypries announced a policy shift when she said Germany would work with the United States to open the files. Officials close to the negotiations said, however, that lingering divisions within the German government and reluctance by the International Committee of the Red Cross had complicated the talks over treaty language. "We were hearing multiple voices," said Paul Shapiro, a member of the US delegation, during a break in the closed-door talks. "But people understand that we are here to reach an agreement. I am encouraged." The proposed changes would give researchers immediate access to the vast storehouse of records at Bad Arolsen, which contain concentration camp registrations, transportation lists and other files that identify some 17.5 million victims, prisoners or slave laborers.