Beijing, China (CNN) -- Some 153 people were trapped in a Chinese coal mine after it was flooded, state-run media reported.

Mine workers became trapped in the Wangjialing coal mine in China's Shanxi Province on Sunday when underground water gushed into the mine, the official Xinhua news agency reported, citing the provincial work safety supervision administration.

More than 100 workers were rescued from the mine, officials said.

The cause of the flooding was not immediately known.

Officials originally estimated that 152 people were trapped inside, then revised that number to 123. But late Sunday, officials revised the number again to 153, Xinhua said.

The mine is a key project approved by the provincial government in a coal-rich area, Xinhua reported.