The unstable “quake lake” which formed as the landslides caused by the tremor stopped the water from its path prompted the Chinese authorities to carry out massive evacuations. China’s Vice Premier Hui Liangyu said the lake is China's "most urgent task" in the aftermath of the 7.9 earthquake which devastated the country, the state-run media reported.

With the help of the Chinese military, the engineers have flown earth-moving equipment and explosives to the site which is situated in China's Beichuan County. The engineers are trying to create a spillway to ease the pressure of the Jianjiang river’s water.

"The Tangjiashan quake lake should be our most urgent task. It is threatening millions of lives in the area downstream and any negligence will cause new disasters to people who have already suffered the quake," Hui said.

Nearly 158,000 people from nearly 170 communities were evacuated by authorities, but the number of evacuees could rise to 1.3 million if the engineers monitoring the lake reach the conclusion that a devastating release of water is imminent, the Xinhua news agency reported.

"It's better for them to complain about the trouble that the evacuation would bring than to shed tears after the possible danger," said Liu Ning with the Ministry of Water Resources.

He added that the landslides are holding back 170 cubic yards (130 million cubic meters) of water.

The operation of creating the spillway will be completed in 10 days, the engineers said.

Chinese authorities released an updated death toll of the earthquake. Beijing estimated the powerful tremor killed at least 68,109. Another 23,150 are missing. More than 420,000 homes collapsed.

The quake also left approximately five million people without home. Several powerful aftershocks have struck the area hindering the relief efforts. The last aftershock hit the area on Sunday killing six other people and wrecking 300,000 more homes.