Before the onset of Operation Reinhard which marked the most deadly phase of the Holocaust in Poland many Jews were transported by road to killing sites such as the Chełmno extermination camp, equipped with gas vans. In 1942, stationary gas chambers were built at Treblinka, Belzec, Sobibor, Majdanek and Auschwitz. After the Nazi takeover of PKP, the train movements, originating inside and outside occupied Poland and terminating at death camps, were tracked by Dehomag using IBM-supplied card-reading machines and traditional waybills produced by the "Reichsbahn". The Holocaust trains were always managed and directed by native German SS men posted with that express' role throughout the system.