Seven Iranian coal miners died in a pit explosion in the northern Caspian Sea province of Mazandaran, a Red Crescent official said on Sunday. District Governor Taqi Derakhshandeh told the official IRNA news agency the explosion on Saturday had been caused by an accumulation of gas. "Seven have been killed," said a Red Crescent official, speaking to state television at the mouth of the mine. IRNA reported 12 men had worked in the mineshaft. The surviving five were all injured. Four people died in a coal mine explosion in Mazandaran in 2001, also caused by a build-up of gas.