Washington's National Zoo says one of its two newborn panda cubs has died just three and a half days after being born.
The zoo said the remaining cub, the larger of the two born on Saturday, appears to be strong, robust and behaving normally, and remains with its mother, Mei Xiang.
This isn't the first time that Mei Xiang has lost a cub.
A second, stillborn cub was also born in 2013, and in 2012, she gave birth to a cub that died after just six days.
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But Mei Xiang does have two other surviving cubs. The first, Tai Shan, was born in 2005, and the second, Bao Bao, turned two years old on Sunday.
The National Zoo is one of only four zoos nationwide to have pandas, which are on loan from China.
The zoo's first pair of pandas, Ling-Ling and Hsing-Hsing, were a gift from China following President Richard Nixon's historic 1972 visit to the country. The pair had five cubs while living at the zoo, but none survived.
The zoo's current pandas, Mei Xiang and Tian Tian, arrived in 2000.
The pair's first cub, Tai Shan, returned to China in 2010, while their second cub, Bao Bao, still lives at the National Zoo.
The latest birth meant that for the first time the zoo briefly had five pandas: Bao Bao, Mei Xiang, the twin cubs and Tian Tian.
