However, it was only a matter of time before the lack of stability of the "forgotten" structures would lead to a need for action after 60 years without maintenance.

In connection with the inspection of access routes to various properties, the city council once again came across a tunnel system in Gebhardshagen at the end of 1999. After an initial risk assessment, an area above the tunnel system - including the school sports field - had to be closed as a precautionary measure due to a possible risk of collapse.

After a further collapse occurred on a private property in Salzgitter-Bad on February 27, 2000, a project group was set up to investigate the entire air-raid tunnel problem. The Department of Public Order was entrusted with the cross-departmental coordination of all municipal activities in connection with researching and eliminating the dangers posed by the air-raid tunnels.

In the period since then, 13 of the 16 known underground air-raid tunnels have been investigated for their hazard potential; the other 3 structures were found to have been buried after the end of the war. The necessary hazard elimination, i.e. the backfilling of the cavities, was completed in spring 2007.