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. Mass or communal burial was a common practice before the development of a dependable crematory chamber by Ludovico Brunetti in 1873. In ancient Rome waste and dead bodies of the poor were dumped into mass graves called puticuli. In Paris, the practice of mass burial, and in particular, the condition of the Cimetière des Innocents, led Louis XVI to eliminate Parisian cemeteries. The remains were removed and placed in the Paris underground forming the early Catacombs. Le Cimetière des Innocents alone had 6,000,000 dead to remove. Burial commenced outside the city limits in what is now Père Lachaise Cemetery. Mass graves at various places like Semmani and Kokkuthoduvai has been found in Sri Lankan Island that are believed to be killing and burial of innocent Tamils by the SriLankan Army along the years of the Civil War between the Sinhalese government and the Tamils. A mass grave containing at least 300 bodies of victims of a Mongol invasion of Kievan Rus' in the year 1238, was discovered during an excavation in 2005, in Yaroslavl, Russia. The Thirty Years' War, in the 17th century, was Europe's deadliest religious conflict. In the Battle of Lützen, 47 soldiers who perished were buried in a mass grave.