In a statement Friday, zoo officials said the necropsy, or animal autopsy, showed no bruising, hemorrhage or obvious birth defects in Kassiu.
Zookeepers reported Kassiu and her mother appeared normal Wednesday morning. But by the afternoon, Kassiu appeared weak and stopped holding onto her mother. The zoo's medical staff examined the baby and gave her fluids, glucose and antibiotics. A neonatologist and pediatrician were also called in, but Kassiu died Wednesday evening.
Zoo officials are waiting on blood and other tests, which could take a few months.
The western lowland gorilla was born March 19 to 13-year-old mother Naku and 27-year-old father Cassius.