WASHINGTON – The National Zoo’s week-old giant panda cub, born last week, died Sunday morning, the zoo announced.

Keepers heard “distressed vocalizations” from the female giant panda, Mei Xiang, at 9:17 a.m. Sunday and realized “this is not right, this is not good,” said zoo spokeswoman Pamela Baker-Masson.

The keepers also realized they had stopped hearing the cub’s healthy squealing, which had been going on for a week and was a good sign of a thriving cub.

Emergency protocols were activated. One keeper moved to try to distract the mother, while another slipped into the den and retrieved the cub with a long-handled “grabber,” zoo officials said.

An on-duty veterinarian was summoned, and the cub was taken to the keepers’ office in the panda house, which is stocked with incubators and other emergency equipment.

The veterinarian, Nancy Boedeker, performed cardio pulmonary resuscitation, administered oxygen with a tiny mask and gave the cub some emergency drugs, zoo officials said. But the animal had no heartbeat, was not breathing, and could not be revived.

“This is devastating news for the entire Smithsonian National Zoo community,” a sombre zoo Director Dennis Kelly said Sunday. “Our staff, our volunteers, the people all over Washington and all over the nation that were following the wonderful announcement of the birth of this cub ...”

The zoo said it was not clear what killed the cub, but a necropsy was scheduled to be performed Sunday night by a zoo veterinarian pathologist, John Roberts. The zoo said it might have some preliminary results by today.

“We’re all very anxious to know what happened,” said chief veterinarian Suzan Murray. “We won’t know that for a little while yet.”

Mei Xiang had been “a fabulous mom, taking very good care of the cub,” Murray said. Indeed Mei Xiang had been holding the cub so close to her body, apparently to nurse it and keep it warm, that zoo officials had scarcely been able to glimpse it on the panda cam that was monitoring the den.

It was the sixth giant panda cub to die at the zoo, going back to the 1980s. A seventh cub was still born. The only cub to survive into maturity has been Tai Shan, who was born to Mei Xiang and Tian Tian in 2005.

Giant panda cubs, like many newborns at the zoo, are extremely fragile.