The reports said more than a dozen injured people had been transferred to hospital after the blast at 12:45 p.m. local time in the Zemestanyurt coal mine in Golestan province.
State news agency IRNA quoted a local official as saying some of the trapped miners may have died in the explosion. A rescue operation was under way.
Iran extracted 1.68 million tons of coal in 2016, an increase on previous years, thanks to an easing of international sanctions. It exports only a fraction of the coal and uses most of it in domestic steel production.
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