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WARSAW, Poland — A fire broke out at an "Escape Room" game location in northern Poland on Friday, killing five teenage girls and injuring a man, authorities said.

Police said the dead were found after firefighters put out the blaze, which began around 5 p.m. at an "Escape Room" venue in Koszalin. Highly popular with teenagers across Poland, the "Escape Room" game has players locked inside a room or building and they must find clues that help them get out.

Interior Minister Joachim Brudzinski said the girls were all 15 years old.

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Monika Kosiec, a spokeswoman for police in Koszalin, said the victims were thought to have been celebrating one of their birthdays. She said a 25-year-old man had been hospitalized with burns and could not be immediately questioned by investigators probing the cause of the fire.

Spokesman for regional firefighters, Tomasz Kubiak, said the bodies were found in a room that was near the fire but was not hit by it.

The Polish state news agency PAP said it had learned unofficially that the girls died from carbon monoxide asphyxiation.

Footage on private TVN24 showed ambulances and fire engines in front of a detached two-story house with a large "Escape Room" sign in front.

Brudzinski ordered fire safety checks to be held at all "Escape Room" locations in Poland.

President Andrzej Duda said on Twitter it was a "crushing tragedy" that five young girls died so early in their lives.

Koszalin Mayor Piotr Jedlinski announced that Sunday would be a day of mourning in the city.