People watch water flow out of Tangjiashan quake lake, which is flooding the low-lying Qushanzhen area in China's Sichuan province on Tuesday. (Kota Kyogoku/Kyodo News/Associated Press)

The once-brimming quake lake in central China was significantly drained on Tuesday, easing fears that it would overflow and wash away the homes of the 1.3 million people who live downstream.

Provincial official Liu Qibao declared a "decisive victory" over the lake, after nearly half of the 250 million cubic metres of water it held was successfully funnelled out of a man-made spillway, according to state news agency Xinhua.

The lake's surface is now about 720 metres above sea level, compared to its previous height of more than 740 metres. Water experts had said the lake needed to fall to 720 or lower to be considered safe.

Hundreds of soldiers had been working around the clock for days to drain Tangjiashan lake, a body of water that formed after debris clogged the Tongkou River in the Sichuan province when a massive earthquake struck on May 12.

About 250,000 of the 1.3 million people who live directly downstream from the lake fled the area days ago in fear of flooding, taking shelter in makeshift camps set up on hills in the area. Those who remained in their homes had been doing evacuation drills to prepare for possible flooding.

Trees, TVs, fridges, bodies float by

The water rushing down the spillway did cause some flooding in low lying communities, including Qinglian, but the damage was not as extensive as feared.

"Everybody feels lucky that it didn't submerge the streets in the neighbourhood," said Wu Zhenxing, a Qinglian resident who remained behind after his town was largely evacuated.

As water roared down the spillway Tuesday, Xinhua journalists reported seeing "trees, barrels, TVs, fridges and the occasional dead bodies of quake victims" sail by in the gushing brown water.

Water had started to seep down the spillway on Saturday, but the flow increased dramatically on Tuesday after soldiers triggered two massive explosions that loosened the debris that was forming a bottleneck in the spillway, Xinhua said.

19 dead found in wreckage of rescue helicopter

Meanwhile Tuesday, Xinhua said searchers had discovered the wreckage of an air force helicopter that crashed in the mountains while ferrying people injured in the earthquake.

The remains of the helicopter's five-person crew and 14 quake victims were found at the crash site near the town of Yingxiu, Xinhua said. The agency said wreckage was spread over a wide area of deep vegetation.

The Russian-designed Mi-171 crashed May 31 near the epicentre of the quake in the Sichuan province town of Wenchuan, after flying into fog and turbulence.

The 7.9 magnitude quake killed 69,146 people, and 17,516 are still missing, according to the latest numbers provided by the government. About five million people were left homeless.

With files from the Associated Press