Melted glass from a tunnel of the formerly used underground area. Between burnt organic material these glasses melted together into a block, were discovered. Glass melts between 850 and 1500 degrees Celsius. Since it was in the present case in a brittle consistency, there must have been a heat degree of several hundred degrees Celsius in the tunnel. These chunks of glass confirm the fire in the tunnel system mentioned in CIOS documents that kept going for weeks, as it made it very difficult to enter the system and also questioned the safety given, the statics. The cause of the fire, which also affected the wooden trembles, planks and the door stick of the tunnels, could not be clarified unequivocally. Many of the tunnels were colored black by the fire and the resulting soot.