Hundreds of rescuers were drilling six shafts in an attempt to reach the different parts of the mine, as well as seeking to clear debris left by an explosion on Jan. 10 that cut the miners off from the surface.
Workers passed a note to the surface on Monday saying they were suffering from toxic fumes and rising water levels but calling on rescuers not to give up. Mine managers have been detained for waiting more than 24 hours before reporting the accident.
The mine in Qixia, a jurisdiction under Yantai in Shandong province, had been under construction at the time of the blast.
Increased supervision has improved safety in China's mining industry, which used to post an average of 5,000 deaths per year. Yet demand for coal and precious metals continues to prompt corner-cutting and two accidents in the southwestern megacity of Chongqing last year killed 39 miners.