There were 247 people working in the Jiangjiawan coal mine when the accident occurred yesterday.
So far, 223 people have been evacuated while 24 others were trapped.
The coal mine, now owned by Datong Coal Mine Group, has an annual production capacity of 900,000 tonnes.
Initial investigation suggests the flooding was caused by water accumulated in a mined-out area of the colliery, state- run Xinhua news agency reported.
Rescue operation for the 24 trapped people was underway.
