Suzan Murray, the zoo's chief veterinarian, said the cub's lungs were not fully formed, leading to a lack of oxygen in the bloodstream and eventually caused necrosis, or a hardening of the liver that proved fatal for the six-day-old cub.
The Washington Post reports the cub's mother, Mei Xiang, seems to be getting back to normal. She recently stopped carrying around a toy zookeepers gave her after the cub died. Mei Xiang's appetite has also returned and the rare black and white bear is again eating a full compliment of bamboo and fruits.
Mei Xiang is 14, middle-aged for pandas, but zookeepers said there's no reason she can't become pregnant again.
2014: The Year in Music [PHOTOS]