The Four Main Gas Chamber and Crematorium Complexes were built in 1942 and operating in 1943. The first two were built completely underground and the killing process was fairly standardized. Jews would be imported into the camp by large trucks. Often too ill to even walk, they would pile in to the undressing area. They were instructed to undress to prepare for a disinfecting shower, and that hot coffee would be waiting for them after. They would then be escorted in to the gas chamber where they were swiftly killed. After the gassing process was complete, the corpses were lifted by elevator to the crematorium area, where their bodies would be burned. The other two complexes followed a similar process, however, their chambers were above ground. But, there was a major issue with their construction: the gas chambers could kill many more people than the crematoria could burn daily. In order to overcome this, according to the Guardian, large pits would be dug, and all the bodies would be placed in it. Then, in place of the ovens, the pit would be lit on fire, burning all of the bodies. This allowed even more people to be killed on a daily basis. These chambers operated until the camp's liberation, during which the Germans destroyed all four of the new complexes.