A mass grave is a grave containing multiple human corpses, which may or may not be identified prior to burial. The United Nations has defined a criminal mass grave as a burial site containing three or more victims of execution, although an exact definition is not unanimously agreed upon. Mass graves are usually created after many people die or are killed, and there is a desire to bury the corpses quickly for sanitation concerns. Although mass graves can be used during major conflicts such as war and crime, in modern times they may be used after a famine, epidemic, or natural disaster. In disasters, mass graves are used for infection and disease control. In such cases, there is often a breakdown of the social infrastructure that would enable proper identification and disposal of individual bodies.