JINAN, July 13 (Xinhua) -- Rescuers have been unable to detect signs of life for 24 miners trapped in a flooded iron ore mine in east China's Shandong Province as rescue efforts entered their fourth day late Wednesday.
Rescuers drilled a 68-meter-deep hole to try and find signs of the miners. The miners are currently trapped in a mine belonging to the Zhengdong Mining Co. The mine is located in the Fangzi district of the city of Weifang, according to the city's rescue command center.
The command center said in a press release issued Wednesday evening that rescuers are still working to drain water and sludge from the mine to get to the trapped workers.
Water levels in the mineshaft remain unstable, although they have decreased, according to the center.
The government of Weifang said 31 people were working underground when the mine was flooded at around 11 p.m. Sunday. Seven of them managed to escape.
Mining authorities said the workers were conducting maintenance work in the mine when the accident occurred.
An initial investigation found that an open-air stone pit located near the mine became filled with water after several days of heavy rain. The pit collapsed, sending an estimated 20,000 cubic meters of water into the mine.
The mine received a production permit in February 2009, with mining operations scheduled to begin this October.