While the recovery effort continues in search of two people in the ruins of the civic archives in Cologne, Germany, officials fear the papers and unpublished works of Nobel Prize-winning author Heinrich Boell have been destroyed forever

Only three weeks ago, city officials were celebrating the handover of Boell's radio play scripts, novels, essays and even school reports after negotiating with the late writer's family for years.

The six-story building collapsed Tuesday after its foundations caved in owing to work being done on a building project nearby. Two men who are missing are believed to have been smothered by the rubble.

'We and the Boell researchers are feeling numb.' —Publisher Helge Malchow

Boell, who captured the Nobel Prize for Literature in 1972, died in 1985. He's considered one of Germany's most popular postwar writers.

Helge Malchow, the head of Kiepenheuer und Witsch, the publisher of Boell's works — including The Clown, Group Portrait with Lady and The Lost Honour of Katharina Blum — confirmed Friday the writer's archival material and unpublished works were held at the municipal archive.

Malchow told The Guardian newspaper the loss would be "unquantifiable."

"If these materials, manuscripts and other original documents really are lost, it will create a hole that will probably never be able to be filled. We and the Boell researchers are feeling numb," Malchow said.

Officials also revealed the archive held photographs and 80,000 letters, including 2,400 written to his wife, Annemarie.

A 'catastrophe for all European historians'

Experts say even if the documents weren't entirely destroyed by the collapse, ground water and soil is seeping into the ruins and that would create mould, which would deteriorate the materials.

It is not believed that any of Boell's papers had been copied into digital form or onto microfilm.

Johannes Fried, a medieval scholar from Frankfurt, said the archives also housed a crucial collection of medieval documents. He called the building's destruction a "catastrophe for all European historians."

Other key documents lost include articles written by Karl Marx, letters by the philosopher G.W.F. Hegel and edicts issued by Napoleon Bonaparte.