Nearly 160,000 people were evacuated downstream from an unstable earthquake-created lake in central China, while the government warned Wednesday that rebuilding after the disaster would be "arduous."

The magnitude 7.9 quake that struck on May 12 sent dirt and rocks tumbling into valleys, blocking rivers that have developed into fast-rising lakes.

Some 158,000 people have been evacuated and dozens of villages emptied in case the newly formed Tangjiashan lake bursts before soldiers and engineers can drain it, the official China Daily said Wednesday.

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The people were being sent to camps like the one outside Jiangyou, where an Associated Press reporter saw 12 to 15 people crammed into each of about 40 government-issued tents pitched on a hillside overlooking the river.

"We were told that so far it is the safest place for us to stay if the dam of the lake crashes," said Liu Yuhua, whose village of Huangshi was one of those emptied. "But we will have to move farther uphill if the situation turns out to be worse."

Troops used explosives to clear debris and helicopters to airlift heavy moving equipment to dig drainage channels from the lake, located about 2 miles above the devastated town of Beichuan.

Premier Wen Jiabao told a meeting of the State Council, China's Cabinet, that handling the danger from the swelling lakes was the "most pressing task" in the disaster recovery effort, the newspaper said.

The government has allocated $28.6 million to deal with the swelling lakes, the official Xinhua News Agency said. Of 34 lakes created by the earthquake in the mountainous province, 28 were at risk of bursting, according to the agency.

Meanwhile, the number of confirmed deaths from the quake climbed toward an expected toll of more than 80,000. China's Cabinet said Wednesday that 68,109 people were killed, with 19,851 still missing.

The country's top economic planning body warned that rebuilding after the quake would be difficult.

"Due to the immense magnitude of loss resulted from the quake, production recovery and reconstruction of the quake-hit region will be arduous in the near future," the National Development and Reform Commission said in a statement Wednesday, adding that major infrastructure had been "severely damaged."

Aftershocks continued to rattle the region, causing more damage and injuries. Two temblors Tuesday caused more than 420,000 houses to collapse in Qingchuan county, Xinhua reported.