Mianyang, Sichuan -- 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 in Sichuan Province.

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

A Mi-26 helicopter carries a bulldozer to the vicinity of the swelling Tangjiashan quake lake in Southwest China's Sichuan Province, May 26, 2008. [Xinhua]

The lake currently holds 130 million cubic meters of water, said Liu Ning, Ministry of Water Resources of China chief engineer, who is in Tangjiashan to oversee the diversion. Its water level was 725.3 meters on Monday, only 26 meters below the lowest part of the barrier, he said.

"Around 100,000 (people) would be evacuated to ensure the safety according to the current drainage plan," Liu told the Shanghai-based Oriental TV.

Photo taken on May 22, 2008 shows an aerial view of quake lakes formed after the May 12 earthquake in Beichuan County, southwest China's Sichuan Province. [Xinhua]

Li Huzhang, an engineer with the armed police force, said three emergency plans had been made to dig out the sluice. He said at least 50,000 cubic meters of debris blockage would have to be removed. Rescuers, however, were aiming to remove 100,000 cubic meters of debris if the weather allowed to minimize the bursting risk.

The water level in the lake rose by 1.6 meters on Monday, a slowdown in recent days, a hydraulic expert at the local observation site was quoted by the People's Daily Online.

As of 9 p.m. on Monday, around 600 engineers and soldiers had gathered at the blockage of the quake lake and were taking turns to work throughout the night.

Because of the lack of tents, some soldiers had to sleep outdoors on the blockage at night.

Helicopters have airlifted professionals and materials for the operation to the blockage at the barrier lake in Beichuan County, Sichuan.

A Mig-26 helicopter transported a large bulldozer from Leigu, near Tangjiashan. By 7 p.m. on Monday, more than 10 diggers and bulldozers and 40-plus tons of relief materials, including tents, drinking water, food and gasoline, had been airlifted to the site.

But experts said more machinery needed to be brought in because of the size of the blockage and the debris was likely to continue to accumulate because of the continuous aftershocks. On Sunday, the area was affected by a strong tremor measuring 6.4 on the Richter scale.

Sunday's adverse conditions 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.

But drizzles projected at Monday night would likely to hamper the work, according to officers at the site.

A contingent of armed police arrived on foot early on Monday to help with the task of draining the lake. The policemen 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 had been evacuated since Wednesday.

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

More than 30,000 residents downstream of Tangjiashan lake have been evacuated to higher ground, according to the Mianyang City government.

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

The Ministry of Water Resources said it had completed an inspection of the damaged waterway embankments in Sichuan by 5 p.m. on Sunday. Plans have been made to address the risks in about 479 damaged embankments, which totaled 686.71 km.

Ministry experts said priority would be given to reinforcing the embankments at Beichuan, Jiangyou and Mianyang in the downstream of the Jianhe River, as water discharged from the upstream quake lake may wash against them.