Rescuers are preparing to dynamite the barrier of a swelling earthquake-induced lake at risk of bursting and threatening thousands of people downstream in southwest China.

Experts have proposed a water diversion channel to drain Tangjiashan Lake, formed by landslides that blocked a river known as the Jianhe after the May 12 earthquake.

Tangjiashan, one of 35 such lakes, is inaccessible by road and can only be reached by foot or air.

Helicopters had airlifted professionals and materials for the operation by 7:49 AM on Monday to the blockage at the barrier lake in Beichuan County, Sichuan Province.

Sunday's adverse weather hampered the operation, but the weather and visibility were fine on Monday morning, said a spokesman with the Mianyang Airport Headquarters for Quake Relief Flight Operation.

A Mig-26 helicopter had carried a large bulldozer from Leigu, near Tangjiashan, which can only be reached on foot or air. By 2:00 PM on Monday, eight diggers and bulldozers had been airlifted to the site.

Meanwhile a contingent of armed police arrived on foot at the Tangjiashan lake area at 12:35 AM on Monday to help with the task of draining the lake. They are to work on the barrier if bad weather and low visibility continue to hamper flights.

The armed police were part of the 1,800-strong force, including People's Liberation Army (PLA) personnel, who started hiking on Sunday toward the lake, 3.2 km upstream from the Beichuan County seat, from which thousands of quake survivors have been evacuated since last Wednesday.

A PLA officer told Xinhua that the soldiers each carried 10 kilograms of dynamite and planned to carry out small scale blasts to drain the swelling water.

The lake dam is in danger of bursting after water levels rose by almost 2 meters on Saturday to 723 meters, only 29 meters below the lowest part of the barrier, which measured 752 meters high.

The risks were heightened as high winds and thunderstorms were forecast for the area Monday and Tuesday and it was hit by a strong aftershock measuring 6.4 on the Richter scale on Sunday.

The lake is holding more than 128 million cubic meters of water and could cause a devastating flood threatening the lives of 1.3 million residents in adjacent areas if the barrier bursts.

More than 30,000 residents downstream of Tangjiashan Lake have been evacuated to higher ground, according to Mianyang City Government.

Altogether 35 barrier lakes were formed by landslides after the May 12 earthquake, which left 65,080 people dead and 23,150 others missing as of Monday noon, according to the Information Office of the State Council.

(Xinhua News Agency May 26, 2008)