(130130) -- DONGNING, Jan. 30, 2013 (Xinhua) -- An ambulance is seen at the accident site of Yongsheng colliery where a coal mine accident happened, in Dongning County, northeast China's Heilongjiang Province, Jan. 30, 2013. Three workers entered the Yongsheng colliery to do maintenance work but fainted due to poisonous gas in the colliery at around 10:30 a.m. on Jan. 29. Rescuers were then sent to the site, but some of them were also poisoned. Seven workers died and six others were still trapped in the coal mine accident, said the the provincial coal mine safety administration on Jan. 30. The rescue work is still underway. (Xinhua) (zc)