Russia’s nuclear energy agency Rosatom confirmed its role in a deadly rocket engine explosion that killed five staff members and burned three others, and sent radiation levels soaring in the Arkhangelsk region of northern Russia. The Guardian reports that Rosatom said the accident was caused during the test of an “isotope power source for a liquid-fueled rocket engine.” The accident caused a spike in radiation levels 20 times higher than normal in the city of Severodvinsk. Russia’s Defense Ministry had initially said just two people had been killed and six others were injured in the mishap. Analysts say the agency was likely testing a Burevestnik nuclear-powered cruise missile mentioned last year by Vladimir Putin.