According to preliminary investigations, if the leakage continues, about 21,000 people downstream could be affected, Xinhua news agency reported.

Rescue efforts are underway, including relocating residents living near the dam and pumping out water from the reservoir.

So far, the water level at the reservoir has dropped by 125 meters and the leakage has been effectively controlled. Experts on site said preparations were not made for a mass relocation of residents at this time.

Since June 16, Hunan has experienced its heaviest rainfall of the year, breaking historical records in some areas.