A trapped miner is helped to walk out of a coal mine after a mud-rock flow accident occurred at the Zhenxing Coal Mine in Hegang City, northeast China's Heilongjiang Province, March 12, 2013. Seven miners had been rescued and 18 others remained trapped after the accident happened on Monday afternoon. (Xinhua/Wang Kai) 

Rescued miners are sent to an ambulance after a mud-rock flow accident occurred at the Zhenxing Coal Mine in Hegang City, northeast China's Heilongjiang Province, March 12, 2013. Seven miners had been rescued and 18 others remained trapped after the accident happened on Monday afternoon. (Xinhua/Wang Kai) 

An ambulance carrying rescued miners leaves a coal mine after a mud-rock flow accident occurred at the Zhenxing Coal Mine in Hegang City, northeast China's Heilongjiang Province, March 12, 2013. Seven miners had been rescued and 18 others remained trapped after the accident happened on Monday afternoon. (Xinhua/Wang Kai)