Throughout Wednesday night, some 150 workers rushed to secure the accident site and begin demolishing neighbouring buildings that were damaged in the collapse.
"We can probably begin the search for the two missing people by this evening, much sooner than we originally thought," city spokesperson Inge Schürmann said.
Though city officials have said it is unlikely anyone survived the accident, Schürmann said several factors affected their chances of making it out of the rubble alive.
“We are working under a lot of pressure,” she added.
The rubble of the building that collapsed on Tuesday afternoon has been covered with tarpaulins to protect the valuable archive documents. Some are more than 1,000-years-old and include items left to the city by figures like composer Jacques Offenbach and Nobel-Prize winning author Heinrich Böll.
North Rhine-Westphalia's state premier Jürgen Rüttgers plans to meet with the Cologne Mayor Fritz Schramma and fire department Chief Stefan Neuhoff at the scene of the accident on Thursday.
Authorities cannot yet confirm whether underground works in the area were connected to the collapse.