Authorities in the southwestern Chinese province of Sichuan say water levels of a lake formed by last month's earthquake are rising to the point where it could flow into a man-made drainage channel.
As of late Thursday, the Tangjiashan lake stood at 739 meters above sea level, just over one meter below the 475-meter long drainage ditch.
But officials are warning that the lake's rising waters are threatening to burst the naturally formed dam. More than one million people are estimated to be in areas that could be inundated if the natural dam breaks.
More than 250-thousand people have already been evacuated from low-lying areas near the lake.
The lake at Tangjiashan has become a pressing issue in the aftermath of the seven-point-nine magnitude earthquake, which killed more than 69-thousand people and left millions homeless.
Premier Wen Jiabao visited Tangjiashan lake Thursday, saying the efforts were reaching a critical moment. Mr. Wen says the most important thing now is to ensure there are no casualties.
Meanwhile, Chinese authorities continued to block access to schools destroyed by last month's earthquake in an apparent effort to quell demonstrations by angry, grieving parents.
Police and soldiers have been deployed outside several schools in Sichuan, where parents are demanding official accountability for what they say is the shoddy construction of the facilities.
Thousands of schools collapsed during the May 12th earthquake and by some estimates more than six-thousand students died.
Chinese officials have not said how many children died in the earthquake.