The 21-year-old Russian sat before a clerk of the U.S. Army Judge Advocate's office, describing the furnaces at Auschwitz, the Nazi death camp where he had been a prisoner until a few weeks previously.

"I saw with my own eyes how thousands of Jews were gassed daily and thrown by the hundreds into pits where Jews were burning," he said.

"I saw how little children were killed with sticks and thrown into the fire," he continued. Blood flowed in gutters, and "Jews were thrown in and died there"; more were taken off trucks and cast alive into the flames.

Today the Holocaust is known in dense and painful detail. Yet the young Russian's words leap off the faded, onionskin page with a rawness that transports the reader back to April 1945, when World War II was still raging and the world still knew little about gas chambers, genocide and the Final Solution.

The two pages of testimony, in a file randomly plucked off a shelf, are among millions of documents held by the International Tracing Service, or ITS, an arm of the International Committee of the Red Cross.

This vast archive — 16 miles of files in six nondescript buildings in a German spa town — contains the fullest records of Nazi persecutions in existence. But because of concerns about the victims' privacy, the ITS has kept the files closed to the public for half a century, doling out information in minimal amounts to survivors or their descendants on a strict need-to-know basis.

This policy, which has generated much ill-feeling among Holocaust survivors and researchers, is about to change.

In May, after years of pressure from the United States and survivors' groups, the 11 countries overseeing the archive agreed to unseal the files for scholars as well as victims and their families. In recent weeks the ITS' interim director, Jean-Luc Blondel, has been to Washington, The Hague and to the Buchenwald memorial with a new message of cooperation with other Holocaust institutions and governments.

ITS has allowed Paul Shapiro, of the U.S. Holocaust Memorial Museum in Washington, to look at the files and has also given The Associated Press extensive access on condition no names from the files are revealed unless they have been identified in other sources.

"This is powerful stuff," said Shapiro, leafing through the file containing the Russian's statement and some 200 other testimonies that take the reader into the belly of Hitler's death machine — its camps, inmates, commandants, executioners and trusted inmates used as low-level guards and known as kapos.

"If you sat here for a day and read these files, you'd get a picture of what it was really like in the camps, how people were treated. Look — names and names of kapos, guards — the little perpetrators," he said.

Moved to this town in central Germany after the war, the files occupy a former barracks of the Waffen-SS, the Nazi Party's elite force. They are stored in long corridors of drab cabinets and neatly stenciled binders packed into floor-to-ceiling metal shelves. Their index cards alone fill three large rooms.

Mandated to trace missing persons and help families reunite, ITS has allowed few people through its doors, and has responded to requests for information on wartime victims with minimal data, even when its files could have told more.

It may take a year or more for the files to open fully. Until then, access remains tightly restricted. "We will be ready any time. We would open them today, if we had the go-ahead," said Blondel.

When the archive is finally available, researchers will have their first chance to see a unique collection of documents on concentration camps, slave labor camps and displaced persons. From toneless lists and heartrending testimony, a skilled historian may be able to stitch together a new perspective on the 20th century's darkest years from the viewpoint of its millions of victims.

"The overall story is pretty well established, but many details will be filled in," said Yehuda Bauer, professor of Holocaust Studies at the Hebrew University of Jerusalem.

"There is a great deal of very interesting material on a very large number of concentration camps that we really don't know much about," he said. "It may contain surprises. We don't know. It has material that nobody's ever seen."

A visitor to the archive comes into direct contact with the bureaucracy of mass murder.

In a bound ledger with frayed binding, a copy of a list of names appears of Jews rounded up in Holland and transported to the death camps. Buried among the names is "Frank, Annelise M," her date of birth (June 12, 1929), Amsterdam address before she went into hiding (Merwerdeplein 37) and the date she was sent to a concentration camp (Sept. 3, 1944).

Frank, Annelise M. is Anne Frank.

She was on one of the last trains to Germany before the Nazi occupation of Holland crumbled. Six months later, aged 15, she died an anonymous death, one of some 35,000 casualties of typhus that ravaged the Bergen-Belsen camp. After the war, "The Diary of Anne Frank," written during her 25 months hiding in a tiny apartment with seven others, would become the most widely read book ever written on the Holocaust.

But most of the lives recorded in Bad Arolsen are known to none but their families.

They are people like Cornelis Marinus Brouwenstijn, a Dutchman who vanished into the Nazi gulag at age 22 for illegally possessing a radio. In a plain manila envelope are his photo, a wallet, some snapshots, and a naughty typewritten joke about women in the army.

After the war, his family repeatedly wrote to the Red Cross asking about him. In 1949, his parents received a terse form letter saying he died sometime between April 19 and May 3, 1945, in the area of a German labor camp. The personal effects, however, remained in Bad Arolsen, and with the family long deceased, there is no one left to apply for their return.

To critics who accuse them of being tightfisted with their information, the Red Cross and ITS counter that they have to abide by German privacy laws and protect the reputations of victims whether alive or dead. They say the files may contain unsubstantiated allegations against victims, and that opening up to researchers would distract ITS from its main task of providing documentation to survivors or victims' relatives.

One area of study that will benefit from the ITS files is the "Lebensborn" program, in which children deemed to have the "proper genes" were adopted or even kidnapped to propagate the Aryan master race of Hitler's dreams.

Another subject is the sheer scope of the Holocaust system. The files will support new research from other sources showing that the network of concentration camps, ghettos and labor camps was nearly three times more extensive than previously thought.

Postwar historians estimated about 5,000 to 7,000 detention sites. But after the Cold War ended, records began pouring out of the former communist nations of East Europe. More sites were disclosed in the last six years in claims by 1.6 million people for slave labor reparations from a $6.6 billion fund financed by the German government and some 3,000 industries.

"We have identified somewhere in the neighborhood of 20,000 camps and ghettos of various categories," said Geoffrey Megargee of the Holocaust Museum in Washington, who is compiling a seven-volume encyclopedia of these detention centers.

The archive has some 3.4 million files of DPs — Displaced Persons. They include names such as John Demjanjuk and Viorel Trifa, who immigrated to the United States and later became internationally known because their role in the Holocaust came into question.

Between 1933 to 1945, the Nazi persecution grew to assembly-line proportions, slaughtering 6 million Jews and an equal number of Gypsies, homosexuals, mental patients, political prisoners and other "undesirables." Tens of millions were conscripted as forced laborers.

To operate history's greatest slaughter, the Nazis created a bureaucracy that meticulously recorded the arrest, movement and death of each victim. Sometimes even the lice plucked from heads in concentration camps were counted.

But as the pace of genocide stepped up, unknown numbers were marched directly from trains to gas chambers without being registered. In the war's final months, the bookkeeping collapsed, though the extermination continued.

What documents survived Nazi attempts to destroy them were collected by the Allies to help people find missing relatives. The first documents were sent in 1946 to Bad Arolsen, and the administration was handed over to the Red Cross in 1955.

Some 50 million pages — scraps of paper, transport lists, registration books, labor documents, medical and death registers — make reference to 17.5 million individuals caught up in the machinery of persecution, displacement and death.

Over the years, the International Tracing Service has answered 11 million requests to locate family members or provide certificates supporting pension claims or reparations. It says it has a 56 percent rate of success in tracing the requested name.

But the workload has been overwhelming. Two years ago it had a backlog of nearly half a million unanswered queries. Director Blondel says the number was whittled down to 155,000 this summer and will disappear by the spring of 2008. New queries have slowed to just 700 a month.

One of ITS' critics is Sabine Stein, archivist at the Buchenwald concentration camp 150 miles from Bad Arolsen. She says the archive's refusal to share its files has caused heartbreak to countless survivors and their descendants.

For instance, in 1989, Emilia Janikowska asked ITS to trace her father, Ludwig Kaminski, a coal miner from Poland who was never heard from again after his arrest in 1939. It took more than three years to send her a standard form reporting Kaminski had died in Buchenwald Dec. 1, 1939.

But there was more she could have been told.

Documents copied by the U.S. Army before they went to Bad Arolsen, which were seen by AP at Buchenwald, include mention of Kaminski. They say he was prisoner No. 8578, that he had arrived in Buchenwald six weeks earlier with 600 other Poles and had been placed in Camp 2. The known history of Buchenwald says Camp 2 was a wooden barracks and four big tents, jammed with 1,000 Poles and Vienna Jews. Dozens of inmates died from the cold that winter. The cause of Kaminski's death was pneumonia.

No one ever told his daughter any of this.

"We had no news from my father since the moment he was arrested," Janikowska said when contacted at her home in Krakow, Poland. She now wants more information for a compensation request.

Archivist Stein says: "Former inmates and their families want to see some tangible part of their history; they want to tell their stories," she said. "What I find most frustrating is that they have all these documents and they are just sitting on them."

Earlier this month, ITS went some way to make amends, delivering a full inventory of its records on Buchenwald and promising to give priority in searching for 1,000 names Stein had requested.

Compounding the delay in releasing the files is the cumbrous makeup of the governing committee. Any decision on their future requires the assent of all 11 member nations — Belgium, Britain, France, Germany, Greece, Israel, Italy, Luxembourg, the Netherlands, Poland and the United States.

Last May's agreement to open the archive stipulates that it will remain off-limits until formal ratification by the 11 governments. After that, each of the 11 countries can have a digital copy of the files and decide who has access to it.

But some delegations are worried the process will take too long, at a time when aged survivors are dying every day.

"What victims of these crimes fear the most is that when they disappear — and it's happening very fast now — no one will remember the names of the families they lost," said Shapiro of the Washington museum, who was a delegate to the talks.

"It's not a diplomatic timetable, and not an archivist's timetable, but the actuarial table. If we don't succeed in having this material public while there are still survivors, then we failed," he said.