The cub was found dead Sunday morning after panda keepers heard sounds of distress from its mother, Mei Xiang.
Staffers were able to retrieve the cub about an hour later. The cub appeared to be in good condition, and there were no outward signs of trauma or infection.
Panda cubs are born about the size of a stick of butter and are delicate infants. They're at risk for infections and are so small that it is not unheard of for panda mothers to unknowingly crush their young.
The cub had been a surprise at the zoo. Fourteen-year-old Mei Xiang had five failed pregnancies before giving birth, and only one panda cub has survived at the zoo in the past.
The Associated Press contributed to this report.