Chinese troops have begun work to drain a lake formed by a landslide during the devastating earthquake in Sichuan province.
With heavy rain forecast for the coming days, experts fear the fast-rising Tangjiashan lake could burst its barriers and flood a town downstream.
More than 100,000 people have already been evacuated downstream over the past week, and if the lake bursts, more than 1.2m others would be at risk.
The swelling body of water is one of about 35 'quake lakes' that could cause huge problems if they burst.
The earthquake has also left 69 dams in the region in danger of bursting.
More than 65,000 people have been confirmed dead following the earthquake nearly two weeks ago.
Today, Taoiseach Brian Cowen signed a book of condolence for the victims of the earthquake at the Chinese ambassador's residence in Dublin.