Soldiers blew up wooden houses and other debris Sunday in a lake formed by China's deadly earthquake to speed the flow of water into a spillway and ease the threat of flooding for more than 1 million people.

The Tangjiashan lake, created when a landslide dammed the Tongkou River, continued to swell even as water gushed down the diversion channel built after two weeks of frantic work by engineers and soldiers.

The spillway is meant to ease the threat of flooding for more than 1 million people in the disaster zone.

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Authorities were still on high alert, although the draining operation was progressing smoothly, the official Xinhua News Agency said.

"There is a lot of debris in the upper reaches, and some are quite big, like wooden houses. So now we have asked soldiers to eliminate the debris by using explosives or other means," Minister of Water Resources Chen Lei told China Central Television.

Soldiers hurled explosives at pieces of splintered wood drifting in one section, according to footage aired during the CCTV noon newscast. Troops also blasted away boulders in the diversion channel, Xinhua reported.

Draining the Tangjiashan lake has become a priority for a government trying to head off another catastrophe as it cares for millions left homeless by the May 12 earthquake that killed nearly 70,000 people. More than 1.3 million people live downriver from Tangjiashan, and 250,000 of them have been evacuated.

Government experts, quoted by state media, played down the threat of imminent flooding, saying Tangjiashan's landslide-created dam should hold. But state media and officials estimated it would be a week before the evacuees could return home, even if all goes well.

The official death toll crept up Saturday to 69,134 people, with 17,681 still missing.

The Tangjiashan lake is the largest of more than 30 created by last month's quake.

Meanwhile, a cargo train derailed in northeastern Sichuan province early Sunday after being struck by rocks falling from a mountain, Xinhua said. One railway worker was killed and another was seriously injured.

It was not known if the falling rocks were related to the earthquake or its aftershocks. The rocks may have been loosened by recent heavy rains, Xinhua reported, citing a Chengdu railway administration official.

Rail traffic was suspended or rerouted, and the damaged line was expected to be repaired in a day.