Chengdu, China ? A powerful aftershock destroyed tens of thousands of homes in central China on Sunday, killing six people and straining recovery efforts from the country’s worst earthquake in three decades. More than 500 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 in Sichuan province and injured more than 480 others, 41 seriously, the official Xinhua News Agency said.

The news agency said Monday that the aftershock also killed four people and injured 20 others seriously in neighboring Shaanxi province.

Some 71,000 homes that had survived the original quake were leveled, and another 200,000 were in danger of collapse from the aftershock that caused office towers to sway in Beijing, 800 miles away.

Xinhua did not give any details on whether the houses were occupied.

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 1,800 police and soldiers hiked with 22 pounds of explosives each to blast through debris, according to Xinhua.

The news agency said the soldiers arrived at the lake early Monday “and immediately began work to defuse the danger of a major flooding.”

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.”