Story highlights Crash happened in Semnan province in northern Iran, east of Tehran

It's not clear what caused the crash

Tehran, Iran (CNN) Two trains collided in northern Iran on Friday morning, killing 44 people and injuring dozens of others, Iran's semi-official Tasnim news agency reported.

Flames blazed and black smoke poured from at least one train car in the province of Semnan, east of Tehran, video distributed by Reuters and official Iranian news channel IRINN showed.

Eighty-two people were injured, Tasnim reported, citing Pir Hossein Koolivand, the country's director of emergency services. All but 17 had been released from hospitals by Friday evening, Koolivand said.

At least one of the trains had passengers, some of whom were burned by the fire, Iran's official Islamic Republic News Agency reported, citing Ali Yahyaei of the Red Crescent Society.

Helicopters and ambulances rushed injured people to hospitals. Frosty conditions slowed firefighters' access to the scene, IRNA reported. Temperatures were below freezing even in the afternoon.

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