A new panda mother who gave birth to twins this week accidentally crushed one of her newborns in her sleep, state media said Friday.

Ya Ya, who lives in the south China's Chongqing Zoo, delivered the twin cubs about an hour apart on Tuesday. One was taken to the Wolong Giant Panda Protection and Research Center, also in Sichuan province while the other cub stayed with Ya Ya.

After falling asleep late Thursday for the first time since her labor, Ya Ya apparently crushed her newborn while it was nursing, the official Xinhua News Agency said on its Web site.

• Click here to read about a giant panda cub born at an Atlanta zoo.

A zoo handler noticed the cub, which weighed only about 90 grams (3 ounces), had fallen away motionless from her mother's nipple, it said. Zoo staff took the cub away while Ya Ya was still asleep and an autopsy showed that its heart, liver and other organs had been crushed.

The report said that Ya Ya searched around for her cub after waking up, then appeared depressed, laying listlessly in her zoo enclosure.

The report did not say if zoo staff would try to reunite the mother with her other cub.

Ya Ya was mated with 11-year-old Ling Ling from Wolong in April. The pandas watched a mating video before breeding.

Last month, the government announced the birth of four sets of panda twins. China has more than 180 pandas living in captivity, according to the government.

A 2002 government census found there were just 1,596 pandas left in the wild. But state media has said a new study by Chinese and British scientists has found there might be as many as 3,000.