A comprehensive conservation program is well under way for Yungang Grottoes, a World Heritage site, in Datong of northern China's Shanxi Province.

Of the program, an anti-seeping project has been recently approved by provincial cultural relics protection authorities, Huang Jizhong, deputy president of the research institute of Yungang Grottoes, told Xinhua Sunday.

The project embraces anti-infiltration efforts for cave roofs, seeping water control and arrangements against rain flushing at cave eaves, according to Huang.

Among the 45 major caves of Yungang, 21 had recorded seeping water, Huang said.

To prevent rains from eroding the Buddhist statues in the caves, an improved drainage system has been established, Huang said.

Apart from weathering caves which mainly resulted from seeping water, the Yungang Grottoes are also threatened by coal dust, as the World Heritage site is at the heart of China's coal belt.

To this end, nearby factories were relocated and truck traffic was rerouted in 1998, and five villages has since moved and trees have been planted around the site.

Yungang Grottoes hold more than 50,000 statues of Buddha dating to 1,500 years ago, their heights ranging from several centimeters to 17 meters.