Beijing (AsiaNews/Agencies) - The authorities are "urgently" removing 99 existing sources of radiation in the valley of lake Tangjiashan, which threatens to burst its banks and flood the valley beneath it, according to Ma Ning, regional head of the office for environmental protection.

The material is removed with cranes, placed inside marked vehicles, and taken at least 300 kilometres from the area at risk in Mianyang.  It is believed that, in addition to material used for X-ray machines or in equipment for checking for defects in buildings and bridges, there are also inactive nuclear power plants, and even a nuclear weapons plant, which might contain extremely unstable elements like tritium, plutonium, and uranium, as well as a nuclear reactor, according to the French institute for radiological protection and nuclear security.

The lake was created by the geological activity that blocked the flow of a river.  The water is rising, and could collapse the dam and flood the area of the valley, where 1.3 million people live.  197,000 of them have already been evacuated.  For days, the army has been digging a channel to drain the water, enough to fill 50,000 Olympic pools, but the work is not expected to be finished before June 5.

The earthquake created another 33 lakes, 28 of which threaten to collapse within a few days, causing flooding.

It is the first time that Beijing has admitted the risk of nuclear contamination caused by the earthquake.  Last week, Zhou Shengxian, minister for environmental protection, said that the 32 "radioactive sources" buried by the earthquake had already been recovered, except for two.

The 15 million people displaced by the earthquake are also facing other unexpected risks.  From a chemical plant in Leigu, near the epicentre, gas has escaped and poisoned four people, forcing more than 800 others to flee.  There are 14,357 companies in the area hit by the earthquake, including 2,900 chemical companies. Zhou says that "thousands" of people are monitoring every possible risk.