Pan Zengwu, deputy chief of the Shanxi provincial coal geological bureau, said rescuers heard what they believed to be the trapped miners making the noise at 2:15 pm.

About 3,000 rescuers are struggling to pump water and reach the trapped miners.

Altogether 14 pumps were pumping up to 1,935 cubic meters of water per hour and additional rescuers were installing one more pump.

The mining zone was estimated to have more than 2.3 billion tonnes of coal reserves, including 1.04 billion tonnes of proven reserves, according to the company's official website.

If the trapped workers cannot be saved, the accident will be China's worst mining disaster in more than two years. In August 2007, a total of 181 workers died at two flooded coal mines neighboring each other -- 172 at one mine -- in Xintai, eastern Shandong Province.