A mysterious explosion at a Russian weapons testing site earlier this month released various radioactive isotopes, creating a cloud of radioactive gases that swept across a nearby town. A Norwegian nuclear expert said that the isotopes – of strontium, barium, and lanthanum – were caused by a “nuclear chain reaction,” saying it was evidence that it “was a nuclear reactor that exploded.”

Thousands of people have attended the funerals of five Russian nuclear engineers killed by an explosion as Russia tested a new rocket engine, a tragedy that caused a large increase of radiation and raised questions about a secretive weapons programme. According to Russian government, radiation levels around the site in Severodvinsk were estimated up to 16 times higher than the norm.