Sayyiduna Abu Hurairah (may Allah be pleased with him) reports that the Messenger of Allah (peace and blessings be upon him) said: There is no blood money for wounds caused by animals, no blood money for one who dies by falling into a well, no blood money for one who dies by falling into a mine, and there is a fifth (khums) in buried treasure (rikaz).
Hadith Referenceالمنتقى ابن الجارود / كتاب الطلاق / 795