CINCINNATI (AP) -- Zoo officials in Cincinnati say they've learned the death three months ago of an endangered Sumatran rhino was caused by liver failure resulting from a disease.

The Cincinnati Zoo & Botanical Garden said Thursday that the ailment (hemochromatosis) left 21-year-old Emi with an excess of iron in her system. Zoo officials say they're not aware of another documented case of a Sumatran rhino dying from the disease, which has been found in other captive wild animals and occurs in humans and domestic animals.

Emi had lived at the zoo for 14 years and was key to its program that successfully produced the first Sumatran rhino calves born in captivity in more than a century. She had given birth to three offspring, starting in 2001.