It said the water poured into the mine through an old shaft.
By 8:50am (0150GM) on Saturday, "the working places under the mine have all been inundated," Xinhua said, citing rescue officials.
Poor safety standards make Chinese coal mines among the most dangerous in the world. About 1,800 coal miners died in accidents during the first half of 2007.
Earlier this month, 69 coal miners were rescued in the central province of Henan after being trapped underground for three days by flooding caused by heavy rain.