By late 1943, production had started. On 10 December, Albert Speer and his staff visited the tunnels, observing the terrible conditions and finding them littered with corpses. Some members of Speer's staff were so shocked that they had to take an extra period of leave. A week later, Speer wrote to Kammler, congratulating him on his success "in transforming the underground installation (...) from its raw condition two months ago into a factory, which has no equal in Europe and which is unsurpassed even when measured against American standards. I take this opportunity to express my appreciation for this really unique achievement and to ask you also in future to support Herr Degenkolb in this wonderful way."