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SS men escorted the men, women, and children selected for death to the gas chambers—initially to the gas chamber in crematorium I and “bunkers” 1 and 2, and, from the spring of 1943, to the gas chambers in crematoria II, III, IV, and V.
Trucks carried those too infirm to walk, and the rest marched. These people had to disrobe before entering the gas chambers. In crematorium I, they undressed either in the yard (surrounded by a wall) or in the antechamber. Wooden barracks were erected for this purpose at bunkers 1 and 2. There were special undressing rooms at crematoria II-V.
When large numbers of transports were arriving in 1944, the people assigned to death in the gas chamber in crematorium V also disrobed in the open air. After the Sonderkommando was quartered in the undressing room in crematorium IV, the people sent to die there undressed in a specially constructed barracks.
The SS men kept the people fated to die unaware of what awaited them. They were told that they were being sent to the camp, but that they first had to undergo disinfection and bathe. After the victims undressed, they were taken into the gas chamber, locked in, and killed with Zyklon B gas.
After they were killed, Sonderkommando prisoners dragged the corpses out of the gas chambers. They cut off the women’s hair and removed all metal dental work and jewelry. Then they burned the corpses in pits, on pyres, or in the crematorium furnaces. (Until September 1942, some of the corpses were buried in mass graves; these corpses were burned from September to November 1942.)
Bones that did not burn completely were ground to powder with pestles and then dumped, along with the ashes, in the rivers Soła and Vistula and in nearby ponds, or strewn in the fields as fertilizer, or used as landfill on uneven ground and in marshes.