To drive the naked people into the execution barracks housing the gas chambers, the guards used whips, clubs, and rifle butts. Panic was instrumental in filling the gas chambers, because the need to evade blows on their naked bodies forced the victims rapidly forward. Once packed tightly inside (to minimize available air), the steel air-tight doors with portholes were closed. The doors, according to Treblinka Museum research, originated from the Soviet military bunkers around Białystok. Although other methods of extermination, such as the cyanic poison Zyklon B, were already being used at other Nazi killing centres such as Auschwitz, the "Aktion Reinhard" camps used lethal exhaust gases from captured Soviet tank engines. Fumes would be discharged directly into the gas chambers for a given period, then the engines would be switched off. SS guards would determine when to reopen the gas doors based on how long it took for the screaming to stop from within (usually 25 to 30 minutes). Special teams of camp inmates ("Sonderkommando") would then remove the corpses on flatbed carts. Before the corpses were thrown into grave pits, gold teeth were removed from mouths, and orifices were searched for jewellery, currency, and other valuables. All acquired goods were managed by the "SS-Wirtschafts-Verwaltungshauptamt" (Main SS Economic and Administrative Department).