Chinese Premier Wen Jiabao made his third visit to the earthquake zone on Thursday to inspect a swelling quake lake.

There are dozens of unstable lakes in the mountainous regions formed by landslides triggered by the recent earthquake. The one in Tang Jiashan, where water levels are threatening to overflow the natural dam, is in critical condition.

A drainage sluice has been built, and hundreds of thousands of people living in the surrounding areas have been evacuated.

Chinese Premier Wen Jiabao told relief workers, most of whom are soldiers, that human safety is the top concern.

"This is a critical moment for the Tang Jiashan quake lake. We will allow no human casualties during the drainage process. It is our obligation to make sure everyone is safe."