Water flooded a pit of Zhengdong Mining Co. Ltd in Fangzi District of Weifang City last night when 28 people were working, the city government said in a press release.
Seven people managed to escape and rescuers were attempting to reach the remaining.
This is the fourth mine disaster in China in 10 days. Rescuers are still searching for 63 miners trapped from three other incidents.
In Shandong's Zaozhuang city, 28 miners were still trapped after an air compressor caught fire on Wednesday.
According to latest reports, three rescue workers died while travelling down to the pit in a scorching shaft.
In the southern Guangxi Zhuang Autonomous Region, rescuers continued to search for 12 workers who were stranded in a coal pit since July 2.
Meanwhile, rescue work has continued for 9 days after a colliery flood trapped 23 workers underground at a pit in Guizhou Province.
Published 11 July 2011, 05:05 IST