Washington (CNN)One of the two panda cubs born this weekend at the National Zoo has died, the zoo said Wednesday.
Baby panda dies just days after birth at National Zoo
"We are sad to report that the smaller of the two panda cubs has died," the zoo said in a tweet on Wednesday afternoon.
Giant panda Mei Xiang delivered two offspring hours apart on Saturday night. Zoo officials said at the time that the cubs were "vulnerable" given their size, but both appeared to be healthy.
Zoo officials said Wednesday afternoon that in the days after their birth, the cubs were "strong" and "vocal" and "showing us no signs of concerns."
To help tend to the baby pandas, zoo leaders explained to reporters that they would "swap" each of the pandas in and out so that Mei Xiang would only have to care for one panda at a time. The National Zoo would care for the panda not with its mother.
Those swaps were described as largely "successful."
But the smaller cub's condition appeared to deteriorate.
"We immediately noticed that the little cub had not increased in weight, appeared weaker and was exhibiting possible respiratory issues," Don Neiffer, chief veterinarian of the Smithsonian's National Zoo, said Wednesday. "Despite extreme efforts on the part of our dedicated staff, we weren't able to change things."
The small panda was prescribed antibiotics and fluids.
"It's obvious we were prepared, but it's not surprising that we're disappointed," he said.
Brandie Smith, the associate director for animal care sciences, said it was not clear that Mei Xiang had done anything wrong in caring for the smaller cub. The mother was 1,500 times larger than the dead baby, making it impossible at times for zoo officials to track the smaller panda's whereabouts. The mom could easily hide the panda under her chin, officials said.
"She never showed us any signs that she was concerned about her infant," Neiffer said.
Mei Xiang has two other offspring: Tai Shan, born in 2005 and who lives in China, and Bao Bao, who is 2.