CHENGDU, China - A powerful aftershock destroyed tens of thousands of homes in central China on Sunday, killing two people and straining recovery efforts from the country's worst earthquake in three decades.
More than 480 others were injured.
Meanwhile, soldiers rushed with explosives to unblock a debris-clogged river threatening to flood homeless quake survivors.
The fresh devastation came after a magnitude 6.0 aftershock - among the most powerful recorded since the initial May 12 quake, according to the U.S. Geological Survey.
The China National Seismic Network said the aftershock was the strongest of dozens in the nearly two weeks after the disaster.
The new tremor killed two people and injured more than 480 others, 41 seriously, the official Xinhua News Agency said.
Some 71,000 homes that had survived the original quake were levelled, and another 200,000 were in danger of collapse from the aftershock that caused office towers to sway in Beijing.
Before the aftershock, the cabinet said the confirmed death toll from the disaster had risen to 62,664, with another 23,775 people missing. Premier Wen Jiabao has warned the number of dead could surpass 80,000.
A mudslide caused by the aftershock blocked a road, but Xinhua said no serious landslides were reported.
Previous landslides loosened by the quake jammed rivers across the disaster area, creating 35 new lakes that placed 700,000 survivors in jeopardy of floods, Vice Minister of Water Resources E Jingping told reporters in Beijing.
The biggest concern was the new Tangjiashan lake in Beichuan county, where some 1,600 police and soldiers were hiking with 10 kilograms of explosives each to blast through debris.
Hazy weather prevented helicopter flights to the area, and forecasts for rain increased the risk that lakes could overflow.
Rain will "not only cause the amount of water going into the lakes to increase, but also influence their normal structure, so the situation is quite serious," said Vice Minister E.
"It is a daunting task because of the unpredictability of when the barrier lakes will burst."
About 20,000 people have been evacuated from the disaster area due to the flood risk, and the total relocated could rise to 100,000, said Liu Ning, chief engineer at the Ministry of Water Resources.
The ministry also said 69 dams in Sichuan are in danger of collapse from quake damage, but reservoirs have been drained to lessen the risk.
Authorities have said the world's largest water project - the Three Gorges dam, located about 350 miles east of the epicentre - was not damaged.
Elsewhere in the disaster zone, people ventured cautiously back to homes to retrieve belongings, but some decided the risk of entering damaged buildings was too great.
In Hanwang, 58-year-old Zhang Heqing was carrying a handful of plastic bags and had planned to go into his apartment block, but the coal mine employee said he had second thoughts.
"I just don't dare to go in," he said. "I live on the fifth floor and the staircase is blocked and you can't even open the doors."
Down the street, retiree Huang Huimei, 75, and her husband were busy stacking pots, pans, chairs and bed boards in a pile for movers to take to the provincial capital of Chengdu, where her son lives.
Her building remained standing but had serious cracks and was not safe for habitation.
She had spent most of the time since the quake caring for her 95-year-old mother.
"I don't know if we'll be back," she said as her husband handed her part of a cooking stove through the front window of their ground-floor apartment.
More than 15 million homes were destroyed in the disaster, and the Chinese government has appealed for tents to help shelter survivors.
Meanwhile, one of two pandas missing since the quake from a major preserve for the endangered animals in Wolong, near the epicentre, was sighted Sunday.
The panda, named Xixi, disappeared before staff could reach it, but was believed safe. The search will continue Monday.