Earlier, David Hawkins, Al Jazeera's correspondent, reporting from the banks of the Chaping river, said: "It has been raining for a couple of hours, increasing the water level in the lakes.

 

"I am downstream from the lakes and muddy water is rolling through here. The level of the river has risen dramatically. But it is still being contained within its banks.

 

"So the [government measures] here have been successful."

 

Debris blocking rivers

 

More than 30 new lakes have formed in the region, caused by debris from the quake blocking river valleys.

 

The most dangerous is Tangjiashan lake, near Beichuan county, and Chinese soldiers have been racing against time to build a channel to divert the rapidly rising waters.

 

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Heavy equipment has been flown in by helicopter to the remote mountain area.

 

Officials hope the operation to drain the lake will prevent the dam from bursting and causing massive flooding.

 

The work has been made all the more urgent with aftershocks continuing to trigger further landslides and forecasts of heavy rains threatening to put more pressure on the lakes.

 

A contingency plan has been put in place to evacuate some 1.3 million more people from towns and villages downstream if the operation to divert the water does not go according to plan.

 

The number of dead from last month's quake has topped 69,000 with nearly 18,000 more still listed as missing and five million people left homeless.