Veterinary pathologists on Thursday blamed liver disease brought on by insufficient oxygen for the sudden death of a six-day-old baby panda born at the National Zoo in Washington last month.
The unnamed female cub, born to giant panda Mei Xiang under a five-year Sino-American panda breeding and research program, weighed just under 100 grams (3.5 ounces) when she died.
"The immediate cause of death of our panda cub was liver disease," said Suzan Murray, the National Zoo's chief veterinarian, as Mei Xiang returned to public view alongside her male partner Tian Tian.
"The pattern of death in the cells within the liver suggests a lack of oxygen, and our pathologists found underdeveloped lungs," Murray told reporters, citing the results of a thorough necroscopy.
"Since the lungs are the organs that take oxygen into the body, it's thought that that impeded the proper absorption of oxygen. The liver cells did not get enough oxygen and then they died, and that was the cause of death."
Mei Xiang—whose appetite and behavior were nearly back to normal in the aftermath of her loss—gave birth on September 16, causing a sensation because of the rarity of panda births in captivity.
Zoo officials wanted Mei Xiang to raise her cub as naturally as possible, while using webcams to keep a close eye on their progress.
Giant pandas are an endangered species. There are only 1,600 in the wild in China and 300 in captivity around the world.
Explore further: Two red panda cubs born at Chicago's Lincoln Park Zoo