JIANGYOU, China (Reuters) - China declared victory over an unstable "quake lake" on Tuesday as floodwaters were released downstream, where hundreds of thousands had been under threat of a second crisis following last month's earthquake.
Waters poured out of the Tangjiashan quake lake, the largest of more than 30 formed by the May 12 earthquake in Sichuan province, after soldiers blasted away rocks, mud and other rubble blocking its path along a sluice.
The muddy brown water swamped low-lying areas in the nearby wrecked town of Beichuan, washing away corpses, family mementoes and valuables along with the rubble.
The toll from last month's 7.9 magnitude quake stands at nearly 87,000 dead or missing, and millions more have been left homeless.
Tuesday's flooding brought more heartache to the displaced. Many said valuables were now lost for good.
"It began flooding early this morning," said shop assistant Zhu Yunhui, 37, who lost loved ones in the quake and said she had kept many tens of thousands of yuan in her home. "Now we can never go back. This is heartbreaking."
Damage in Beichuan from the tremor was so extensive that authorities have decided to rebuild the town at a site dozens of kilometers away and to make the original county seat an earthquake memorial.
Sichuan's Communist Party chief Liu Qibao described the quake lake breakthrough as a "decisive victory" after the water level in the dam fell by more than 20 meters, Xinhua news agency said.
"... The number of people under threat downstream the lake have dropped from 1.3 million to less than 50,000," Liu was quoted as saying.
Water from the Tangjiashan lake, created when landslides triggered by the quake blocked the flow of the Jianjiang River, has so far prompted the evacuation of more than 250,000 residents downstream in case the mud-and-rock dam burst.
"... So far everything is happening within expectations. As things are, we don't expect to have to evacuate any more," Zhou Hua, spokesman for the lake relief operation, told Reuters.
More than half of the lake's 250 million cubic meters of water had been discharged from the lake as of 0900 GMT, flooding some evacuated villages, farmland and roads but causing no casualties so far, Xinhua said.
Still, PetroChina said it had shut its main fuel pipeline in western China as a precaution against any damage that could result from the rush of water.
Trees, cars and fridges were swept away by the torrent.
The army set up rocket launchers at several points along the route of the floodwaters to defuse the threat posed to dams and bridges, including a key railway bridge, by any big objects in the water, state television said.
Xinhua attributed the abrupt increase in water discharged from the lake to "two massive blasts on Monday evening which broke through the bottleneck" of a sluice opened by soldiers.
Further downstream near Mianyang, the waterway had widened to several hundred meters across.
In Jiangyou, a city sandwiched between Beichuan and Mianyang, hundreds of locals stood on a ridge above the river observing the flow with a mixture of anxiety and curiosity.
But while the river was still a powerful torrent, the water level appeared to be going down.
Rescuers meanwhile found a relief helicopter, carrying 19 quake survivors, medical workers and crew, that crashed near the epicenter of the quake on May 31. There were no survivors.
Authorities also confirmed the death of Mao Mao, a nine-year-old female giant panda, in the famous breeding centre at the Wolong reserve, near the quake's epicenter, Xinhua said.
Mao Mao was one of six pandas that went missing after the tremor ruined the breeding centre and killed five staff workers. The other five pandas had been found alive. The centre will be rebuilt at a new site within the Wolong reserve, Xinhua said.
A 5.2-magnitude earthquake jolted Inner Mongolia autonomous region on Tuesday, while a 5.5-magnitude tremor rocked the northwestern province of Qinghai hours later, Xinhua said. There were no immediate reports of casualties.
Additional reporting Guo Shipeng; Writing by Guo Shipeng and Lindsay Beck; Editing by Jeremy Laurence