JOHANNESBURG, South Africa -- Harry Oppenheimer, former head of the De Beers diamond and Anglo American gold mining companies and one of South Africa's prominent Thoroughbred owners and breeders, died on Aug. 19 in a Johannesburg hospital, the Associated Press reported Monday. Oppenheimer was 91.

Cause of death was not immediately known, though the AP report said that Oppenheimer had been admitted to the hospital on Aug. 18 after complaining of abdominal pains and a severe headache.

Oppenheimer and his wife, Bridget, are listed among South Africa's leading owners and breeders and stand the successful stallion Fort Wood, a son of Sadler's Wells. Most recently, the Oppenheimers' home breeding program - based at their Mauritzfontein Stud near Kimberley, South Africa, where De Beers was founded - produced South African Triple Crown winner Horse Chestnut. Horse Chestnut, 1999's South African Horse of the Year and winner of Gulfstream's Grade 3 Broward Handicap.