Blood Money (Ad-Diyat)
Bukhari :: Book 9 :: Volume 83 :: Hadith 47
Narrated Abu Huraira:
Allah's Apostle said, "There is no Diya for persons killed by animals or for the one who has been killed accidentally by falling into a well or for the one killed in a mine. And one-fifth of Rikaz (treasures buried before the Islamic era) is to be given to the state."