BEIJING - Managers of the Palace Museum admitted on Sunday that a piece of 1,000-year-old porcelain among its invaluable collection had been damaged by error during research, which involved examining the artifact with an analytical device.

This disclosure came after a netizen on Saturday blew the whistle on the accident and claimed the Beijing museum, also known as the Forbidden City, had been trying to cover up the incident.

The porcelain plate, a grade-one cultural relic from the Ge kiln called "Celadon Plate with a Mouth in the Shape of Mallow Petals", was crushed and damaged on July 4 when a laboratory researcher used a device to examine it, according to a statement from the museum.