Steps have been taken to reduce the risks of "quake lakes" -- formed by landslides that blocked rivers -- before the rainy season starts or further aftershocks, officials said on Thursday.

"There are 34 such lakes in the disaster-hit region. The quake lake in Beichuan county is the most dangerous," said Yin Yueping, deputy chief engineer of China Geological Survey.

The lake was formed because massive landslide partially blocked the Qianjiang River upstream of the devastated Beichuan county seat. It is 40 m deep and contains about 30-40 million cu m of water.

Yin said people living downstream of the quake lake in Beichuan have already been evacuated.

Zhu Bing, deputy head of the water resources authority in Sichuan, said on Thursday that the province has been closely monitoring such lakes and formulated emergency response plans, including evacuating people to safer places and blasting or digging of sluices to discharge water.

Experts warned that further aftershocks and rainy weather next month could lead to formation of more quake lakes.

Liu Yuan, deputy head of the geological environment department of the Ministry of Land and Resources, said the water levels of some quake lakes had risen, threatening vast areas.

In 1933, three newly-formed lakes burst their banks 45 days after an earthquake measuring 7.5 on the Richter scale struck Diexi in western Sichuan in August.

The Ministry of Land and Resources and the Ministry of Water Resources have sent experts to check and assess the condition of the lakes.

Yun Xiaosu, vice-minister of land and resources, told the conference that the ministry is mobilizing all its staff nationwide and will dispatch 500 more experts to the disaster-hit areas to help supervise geological or secondary disasters.

Yun said that provinces such as Sichuan, Shaanxi and Gansu are often struck by landslides and cave-ins due to their peculiar geological structure characterized by high mountains and deep valleys.

Nearly 5,000 geological risks were identified in the 41 counties in the disaster-hit region before the earthquake, Yun said.

Yun said that the ministry would send 100,000 alarm sets to warn people against landslides and cracks in the disaster-hit region.

(Xinhua News Agency May 23, 2008)