Nine people have been arrested for robbing the ancestral tombs of China's first emperor, Qin Shihuang, whose mausoleum is guarded by the terracotta warriors.
Officials say hacksaws were used on the resting places of the emperor's parents and grandparents in north-western Shaanxi province.
Reports say damaged coffins were found and relics taken from the tombs.
Officials say they also discovered a 30-metre tunnel leading into the mausoleum.
The raided mausoleum lies in the ancient Chinese capital of Xian, where China's earliest leaders are buried.
Nearby is the resting place of Emperor Qin, who unified the country in 221BC.
His mausoleum is guarded by the terracotta warriors, which are believed to protect the emperor in the afterlife.
Though discovered last month by guards, the robbery has only now been reported.
The tomb was discovered in 1974.