The tombs, found in the Xinjiang Uygur Autonomous Region, contain wooden caskets with desiccated corpses, along with stoneware, pottery and copper ware believed to have been buried as sacrificial items, Ai Tao from the Xinjiang Archaeological Institute said.
The cluster, believed dating to the Tang Dynasty (A.D. 618-907,) covers an area of 1,800 square yards atop a 65-foot cliff, an unusual location for tombs, Ai told China's state-run Xinhua news agency.
Archaeologists said they were surprised to find such a large number of infant corpses in the tomb cluster, unearthed during construction of a hydropower project.
"But further research is needed to determine why so many people from that tribe died young," Ai said.
The area where the tombs were found was an important stop on the ancient Silk Road that created economic and cultural exchanges between China and the West, the researchers said.