The panda cub born at the National Zoo last week has died, officials said.

The unnamed cub was last heard vocalizing shortly before 9 a.m. Sunday. At about 9:17 a.m., zookeepers and volunteers heard the mother, Mei Xiang, make a honking noise, which was determined to be a distress call.

Staff immediately implemented emergency procedures, zoo officials said. Mei Xiang was distracted, and the cub was retrieved with the aide of a tool resembling a lacrosse stick.

A veterinarian determined that the cub was not breathing and did not have a heart beat. Although she performed CPR, the cub was pronounced dead at about 10:30 a.m.

"This is devastating news for the entire Smithsonian National Zoo community, 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." Dennis Kelly, the zoo's director, said.

Officials said the cause of death was not immediately known. There were no visible signs of trauma and no signs of disease. The cub weighed about 100 grams, which is normal.

"The cub was just beautiful," said Suzan Murray, the zoo's chief veterinarian.

The Mei Xiang was "doing fine," Murray said Sunday early afternoon, and she is being watched closely. The panda house will be closed until officials determine she is safe and healthy, Kelly said.

The cub was born late on Sept. 16 after an artificial insemination procedure in April.

The birth took place after Mei Xiang endured five failed pregnancies, though she gave birth to Tai Shan in 2005. That panda was the first to survive at the Northwest Washington zoo for more than a few days, though the complex first received pandas in 1972.

(View more photographs of Mei Xiang and Tai Shan)

Animal experts had warned that a panda's first weeks of life could be perilous, though zoo officials said last week they were cautiously optimistic about the cub's prospects.

Visitors at the zoo on Sunday were saddened to hear of the cub's death.

"It's unfortunate," said David Edrich, who is from Long Island. "There's only so many of them in the world."

The cub's gender and hopefully the cause of death will be determined during the necropsy and subsequent workup. It will not be named posthumously.

Staff Writer Alan Blinder contributed reporting.