Eventually the Nazis created a more secluded and organized method of killing. Six extermination centers were established in occupied Poland where large-scale murder by gas and body disposal through cremation were conducted systematically. Victims were deported to these centers from Western Europe and from the ghettos in Eastern Europe which the Nazis had established. In addition, millions died in the ghettos and concentration camps as a result of forced labor, starvation, exposure, brutality, disease, and execution.