One tool the museum is preparing is a search engine it plans to make accessible soon on the Internet. It will allow people to search through a separate, limited index of the archive and get a sense of what kind of documents exist. That index describes tranches of the documents, where they came from and where they are stored. It could provide clues about whether the information users are seeking might be there.

Though the museums' researchers can begin working with the material immediately, the public must wait for legal formalities to conclude — which could take several more months.

Unlocking the archive required all 11 countries to amend their international treaty. France, Italy and Greece have yet to complete the process. The others on the commission are the United States, Israel, Britain, Netherlands, Belgium, Poland, Luxembourg and Germany.

Bloomfield called on three countries which have not ratified to do so urgently.

Historians believe the files, which contain information on some 17.5 million individuals, will add texture to the narrative of misery in the camps, where millions of people were worked to death or were simply exterminated with industrial efficiency. Six million Jews died in the Holocaust, one of every three Jews on Earth.

The Associated Press has been given repeated access to the archive in Bad Arolsen in recent months. Random searches through its 16 linear miles (kilometers) of files revealed a wealth of mundane yet telling detail on life and death in the camps.