NANNING - Initial expert analysis showed a land subsidence in south China's Guangxi Zhuang Autonomous Region may be caused by underground water drainage in the region's karst landscape.

The depletion of underground water supplies may also lead to the collapse of the karst landscape and thus increase the chance of land subsidence, said Ma Rongguang, a senior engineer at Guangxi Electric Power Industry Investigation Design and Research Institute.

Investigation into the cause of the accident was still underway.

There were no reports of injuries, but a total of 844 villagers were evacuated after the land sank near a middle school in the Tanluo township, Xixiangtang district of Nanning, capital of Guangxi.

The sink hole was 1.5 meters deep and 2.5 meters wide and has caused one building to collapse, six to tilt and another to crack, according to local authorities.

Prior to the incident, the school had hired workers to drill a 70-meter-deep well for drinking water because of a water shortage, local officials said.