Coal miners react following an explosion in a mine in Azadshahr, in northern Iran, leaving dozens of miners trapped on May 3, 2017. The mine in Golestan province collapsed when trapped methane gas exploded as workers tried to jump-start a locomotive engine, according to reports. (Xinhua/AFP Photo)

TEHRAN, May 3 (Xinhua) -- At least 21 miners were killed and scores injured in a coal mine explosion in the northern Iranian province of Golestan on Wednesday, state TV reported.