Preliminary findings are expected on what killed a week-old giant panda cub at the National Zoo in Washington.

The unnamed cub was found dead Sunday. A necropsy was performed and the zoo was set to present preliminary findings Monday on the cause of death.

Zoo officials said the 4-ounce cub showed no obvious signs of distress before making its final recorded noise Sunday morning. But the cub's mother, Mei Xiang (may shahng), made an unusual honking sound that her keepers interpreted as a distress call.

When the cub was picked up, the animal was not breathing and its heart had stopped. A veterinarian attempted CPR, but the panda cub could not be revived.

Associated Press