A baby giant panda born just one week ago at the National Zoo in the US capital died on Sunday of still to be determined causes.
Panda keepers and volunteers "heard a distress vocalization from the mother, Mei Xiang, at 9:17 am and notified the veterinarian staff immediately," zoo officials said.
"The staff were able to safely retrieve the cub for an evaluation at 10:22 am. Veterinarians immediately performed CPR and other life-saving measures but the cub did not respond," the statement said.
At a first observation, veterinarians said there was no outward sign of trauma, no outward sign of infection, and the cub was "in good body condition" weighing just under 100 grams.
"The National Zoo community mourns the loss of the giant panda cub," the statement read, adding that mother panda Mei Xiang "is under close observation."
Zoo officials immediately turned off the "panda cam," the internet-accessible 24-hour camera trained on the animals.
Mei Xiang, on loan to the Smithsonian-run zoo from China, gave birth to the cub on September 16.
Zookeepers had chosen to keep a physical distance from Mei Xiang, in order to let her raise the cub naturally.
Giant pandas are rare and endangered, with as few of 1,600 surviving in the mountain forests of central China. More than 300 others live in zoos and breeding centers, mostly in China.