This was an industrial method of genocide. Millions of Jews who had been confined to diseased and massively overcrowded ghettos were transported (often by train) to death camps, where some were herded into a specific location (often a gas chamber), then killed with either gassing or shooting. Other prisoners simply committed suicide, unable to go on after witnessing the horrors of camp life. Afterward, their bodies were often searched for any valuable or useful materials, such as gold fillings or hair, and their remains were then buried in mass graves or burned. Others were interned in the camps where they were given little food and disease was common.