People visit a public exhibition of Chinese cultural relics returned by French private collectors, at Gansu Provincial Museum in Lanzhou, capital of Northwest China's Gansu province, July 20, 2015. [Photo/Xinhua]

Chinese cultural heritage authorities began seeking their return in 2005, and they reached an agreement with their French counterpartsthis year after long negotiations.

Pinault transferred his donation to the State Administration of Cultural Heritage in April, and Deydier took his collections to China in May.

Li Xiaojie, director of the State Administration of Cultural Heritage, said the return showed the determination of two culturally resourceful countries to take responsibility and build an international framework to protect cultural heritage.

Maurice Gourdault-Montagne, French ambassador to China, said, "Cultural exchange is always an important cornerstone of communication between two countries".

"Thanks to the private collectors' moves, local people are able to see their own treasures in their homeland," he said.

Song said that the lack of direct evidence was another hurdle to repatriating the lost treasures. A major archaeological project at Dabuzi Hill has created a solid foundation for comparative academic research, he said.