As of late afternoon yesterday, the water level of the lake stood at nearly 742 metres, 2 metres higher than the run-off channel, state television said. The water has been rising 4-5cm an hour since Saturday morning.

Soldiers gave Mother Nature a push by firing several missiles to break up boulders. The flow increased noticeably after the missiles found their target, and water was draining at a rate of about 30 cubic metres per second as of late afternoon yesterday.

Rainfall, landslides and aftershocks could present a problem for draining the lake, which engineers hope to accomplish in a controlled way, Minister of Water Resources Chen Lei said.

There are fears that if water is released too quickly from the lake, for example by blowing open a larger hole, the flow might erode the drainage channel, creating a steeper, narrower course that would pull in water more rapidly, potentially causing the dam to collapse, the Associated Press reported.

An aftershock shook the dam holding back the lake for 20 seconds and caused landslides on surrounding hills early yesterday evening, Xinhua said. The US Geological Survey reported a magnitude 5 earthquake, its epicentre 70km northwest of Mianyang, Agence France-Presse reported.

The effect on the lake was not immediately known.

The earthquake zone experienced 177 aftershocks in the 24 hours before noon yesterday, the China Earthquake Administration said.

In a positive sign, however, the skies cleared over the region and the provincial weather bureau said conditions would remain fine today. But rainfall later this month and in July could pose a challenge.

Upstream from the lake, soldiers have used explosives to break up floating debris to prevent blockages that could impede the flow.

'Some of the floating debris is very large, including wood and wooden houses. The purpose of this is to increase the strength of the flow on the lower reaches,' Mr Chen said.

Soldiers have also widened the existing 475-metre channel by several metres and carved out another with 30 bulldozers and excavators, prompting one official to predict that the threat from the lake could be eliminated in a few days.

Mianyang now resembles a ghost town, with empty streets and many businesses closed after city authorities warned of a possible evacuation.

At the city's stadium, which sheltered tens of thousands of people immediately after the earthquake, many families had left.

'We have nowhere to go,' said one 13-year-old girl, who was still having to sleep beneath the eaves of the stadium.

At a glance

69,136 confirmed dead

17,686 missing

374,061 injured

44.03b yuan in donations received from home and abroad

Source: Xinhua