Eyewitnesses interviewed by the local Koelner Stadt-Anzeiger newspaper drew comparisons with an earthquake and the 9/11 terrorist attacks after the archive building suddenly fell apart on Tuesday, March 3. Two neighboring multi-story apartment houses were also reported to have been destroyed in the incident.

Initial reports said that some 30 people had been trapped in the rubble, but miraculously most of the people inside the buildings seemed to have escaped unharmed. Authorities said the whereabouts of at least two people remained unknown.

Some 200 emergency workers arrived on the scene shortly after the collapse, cutting off water and gas mains.

The archive was built in the 1970s, and there was initially no clear answer to the question of why it would suddenly collapse.

Subway not at fault, company says

Eberhard Illner, a former archive employee, told German radio station Deutschlandfunk the collapse was a "foreseeable catastrophe" and that he had noticed cracks in the building's basement walls.

There was considerable speculation in the media that nearby construction on a subway may have caused the destruction, with some unconfirmed reports that subway tunnels had been filled with massive amounts of water. Work on underground rail tunnels was blamed for the near-collapse of a church in 2004.

The local subway company denied that the building work in the archive could have been at fault. It said that work on tunnels under the site had already been completed and that there was construction going on in the building itself.

"I am not aware of any work occurring at the moment that could have caused this," said Gudrun Meyer, a spokeswoman for the Nord-Sued subway company, told German television station n-tv.

Cologne's archive contains some 65,000 documents connected to the city's history. Some material in the archive dates back to 922.