The leak began Thursday at the Qingxi No. 1 Gas Well in Qinxi, a town in Sichuan Province, Xinhua said.

The first attempt to stop the leak failed yesterday because of "complicated conditions at the well," it said without giving details.

Workers unsuccessfully tried to fill the well with about 200 tons of cement, Xinhua said.

Some 11,200 residents have returned home, but the rest were still stranded because their houses are within 500 meters of the well, which is owned by the state-run China Petrochemical Corp, or Sinopec.

Xuanhan County, where the well is located, is about 500 kilometers northeast of the provincial capital of Chengdu and is one of China's major natural gas bases.