HARBIN - Seven workers died and six others were trapped in a coal mine accident in Northeast China's Heilongjiang province,the provincial coal mine safety administration said Wednesday.

Three worker entered the Yongsheng colliery in Dongning County to do maintenance work but fainted due to poisonous gas in the colliery at around 10:30 a.m. Tuesday, the administration said.

Rescuers were sent to the site, but some of them were also poisoned.

The rescue work is still underway on Wednesday.