Cologne, Germany - Three people were still missing on Tuesday evening several hours after the western German city of Cologne's historical archives and two neighbouring buildings collapsed in what one witness compared to a 9/ll scene.

Earlier, police had spoken of nine missing, but in the meantime six persons had been located elsewhere. A police spokeswoman said sniffer dogs were still being used to search the rubble for those still missing.

But there were fears about their survival chances beneath the rubble.

"A quick rescue is not possible," according to the director of Cologne's fire department, Stefan Neuhoff. It was unlikely that there were any air holes in the rubble.

Speculation about the cause of the collapse is focused on new building work for the city's underground transit system, which runs directly below the archives.

"The complete area was shrouded in a dark mist, just like September 11," said Paraskevi Oustampasiadi, whose newspaper stand is near the collapsed buildings.

Besides the possible human casualties, the damage to the city's historical archives - documenting Cologne's development over its 2,000-year history was immense.

Eberhard Illner, a former long-time department director in the archives, told German radio that the damage was comparably greater than that suffered in the fire of the historic Anna Amalia library in Weimar several years ago.

"We are talking here of about 18 kilometres of shelves of the most valuable archive material, and that on a European standing," he said.

There were fears that the scope of the disaster may be even greater if important literary documents from the estate of late 1972 Nobel Prize winning author Heinrich Boell
(1917-1985) were also in the building.

Cologne's city archives in February had just purchased the remaining 6,400 Boell manuscripts, letters and other documents from the writer's family, giving the city archives possession of the entire literary estate of the Cologne writer.

But it was not immediately known whether any of the Boell estate documents had yet been deposited in the building which collapsed. (dpa)