The aerial photo taken on May 26, 2008 shows the landslide mud that formed the Tangjiashan quake lake near Beichuan County in southwest China's Sichuan Province. The earthquake-induced lake is at risk of bursting and threatening thousands of people downstream. (Xinhua/Zhu Wei)

CHENGDU, May 27 (Xinhua) -- Chinese emergency workers are aiming to evacuate another 80,000 people from the area downstream of a swelling earthquake-induced lake by midnight on Tuesday.

Altogether 158,000 people will have to move from their homes if Tangjiashan Lake bursts its banks. So far, more than 70,000 people in Mianyang City have been relocated.

Two other plans require the relocation of 1.2 million people if half of the lake volume is released, or 1.3 million if the barrier of the quake lake fully opens.

On Tuesday, at least 600 engineers and soldiers were working around the clock to dig a sluice for the blockage with the aid of 29 excavators and bulldozers.

Several Mig-26 helicopters airlifted more machinery to the quake lake. To speed up the project, the helicopters took off under a visibility of 600 meters when the required visibility was 5,000 meters, sources said.

At 5:15 p.m. on Tuesday, rescuers blasted several tree trunks mixed in the blockage. By that day, at least 20,000 cubic meters of debris had been removed.

Zhu Guoliang, an armed police brigadier, said "the soldiers working in Tangjiashan have at least three years experience in this kind of project, and they are seizing every minute to remove the rocks".

He said the sluice would be ready in about three to five days. At least 50,000 cubic meters of debris would have to be removed to build the diversion channel on the blockage body. Rescuers, however, were aiming to remove 100,000 cubic meters of debris if the weather allowed.

The lake is some 3.2 kilometers away from the seat of Beichuan County, the area worst hit in the devastating quake on May 12. It was formed by landslides that blocked a river known as the Jianjiang after the quake, according to Mianyang quake relief headquarters.

People from 169 communities in 33 townships of Mianyang are threatened by the quake lake.

The evacuation was necessary because the water level in the quake lake has continued to rise and the diversion channel won't be in place until June 5, experts with Mianyang quake relief headquarters said on Tuesday.

Tangjiashan, the biggest of 35 lakes formed in the quake, is inaccessible by road and can only be reached by foot or air.

It holds about 130 million cubic meters of water, said Liu Ning, the Ministry of Water Resources chief engineer, who is at Tangjiashan to oversee the diversion work. Its water level was 727.02 meters on Tuesday, up 1.82 meters from Monday and only about 25 meters below the lowest part of the barrier.

Source: Xinhua