A vast archive of documents linked to the Holocaust said Monday it would preserve 300,000 original prisoner files from the Dachau concentration camp in Germany that are disintegrating.

The International Tracing Service (ITS) in the western German town of Bad Arolsen uses its vast trove of historical records to help victims of Nazi persecution and their families and make them available to researchers.

It said the brittle, yellowing files from the Dachau camp in southern Germany included prisoner identification, personal effects and camp registration cards dating from between 1934 and 1945.

The preservation process known as deacidification involves boosting the pH level of the paper, providing lasting protection from decay for invaluable historical records.

As most of the files have already been digitised, the procedure mainly covers documents that are only rarely physically handled.

"The conservation efforts are carried out in accordance with a priority list compiled in 2000, according to which documents of prisoners from concentration camps, prisons and ghettos are given priority treatment," ITS said in a statement.

"Since the beginning of the conservation effort 2,654,586 objects were processed and conserved," out of a total of 30 million held by the archive.

ITS said a similar programme for the Buchenwald camp in central Germany was recently completed, including more than 234,000 individual documents on female prisoners.

The organisation's documents relate to persecution under the Nazis and the mass emigration that took place in the wake of World War II.

ITS is operated under the jurisdiction of an 11-country commission and run by the International Committee of the Red Cross.

The Nazis opened Dachau as a concentration camp for political prisoners in March 1933, just weeks after Adolf Hitler took power. It was the first such site in Germany and served as a model for all the camps to follow.

More than 200,000 people from across Europe were held at Dachau until its liberation by US troops in April 1945, and 41,500 prisoners died there.

[An employee of the International Tracing Service (ITS) works in the ITS files department in 2006. AFP Photo/Martin Oeser]