According to the results of a necropsy, officials say, "her lungs were poorly developed and likely caused her to have insufficient oxygen, which would be consistent with the changes in the liver." The cub was only about a week old.
As for Mei Xiang, the mother, officials add that:
"We are happy to report that Mei is almost completely back to her old self! Her hormones have returned to normal levels, as has her behavior. Mei is choosing to go outside in the mornings. In the afternoons she can usually be found napping on her indoor rockwork. Mei's appetite has also returned, and she is eating almost all of her bamboo and all of her leaf eater biscuits and produce."