Eventually, the Nazis were killing so many people at Auschwitz-Birkenau that they had three buildings with crematoria designed by specialists from Topf und Söhne. At Auschwitz, prisoners worked every hour of the day to destroy corpses. However, people were being gassed so quickly that not every body could be destroyed in the crematoria. Some corpses were also burned in an open air fire pit.<ref name="B/G-199"></ref>