Cologne, Germany  - Rescue teams Wednesday morning restarted the search for missing people after the collapse of the western German city of Cologne's historical archives centre and two neighbouring buildings.

Overnight, police lowered the number of missing people to two, while other reports still spoke of five missing. Earlier, police had spoken of nine missing, but subsequently lowered the number.

Rescuers worked during the night to prevent the building from subsiding further, while firemen started to retrieve documents from the basement of an adjoining building which was not destroyed in the collapse, a fire brigade spokesman said.

A police spokesman said sniffer dogs used to search the rubble for those still missing may have detected victims. Rescue efforts, however, could only begin when rubble from the roof has been removed, for which heavy machinery was necessary.

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.

Meanwhile, staff members accused the city authorities of having ignored earlier reports of damage to the building.

"A technician must be really stupid if such reports are not taken seriously," Eberhard Illner, a former long-time department director in the archives, was quoted as saying by the online edition of the Koelner Stadt-Anzeiger newspaper, accusing the authorities of grave neglect.

City authorities, however, rejected the accusations, saying that earlier expert studies dating from December 2008 said that cracks in the building did not affect the building's structural integrity.

"According to today's knowledge, the damage detected back then was not the cause of the accident," chief city administrative officer Guido Kahlen said.

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.

Illner told German radio that the damage was greater than that suffered in a fire at 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," he said. (dpa)