An explosion Thursday during a rocket engine test that caused radiation levels to jump in northern Russia killed five nuclear workers, the country's nuclear energy agency said. It was the first official word that the agency, Rosatom, was involved, Reuters reports. Three other employees were injured, the agency said. Russian news agencies reported that rocket's fuel caught fire after the test, near the White Sea, and that the explosion threw several people into the sea. "Searches continued as long as there was hope to find survivors," Rosatom's statement said. The tests involved "isotope power sources" on a liquid propulsion system, the agency said, though it added nothing about a radiation release.
Rosatom’s explanation could fit with testing for the Burevestnik, a nuclear-powered cruise missile that Russian President Vladimir Putin referred to in a speech last year, per the Guardian. The Nyonoksa installation conducts tests for Russian navy missile systems, per the BBC, including intercontinental ballistic missiles, cruise missiles and anti-aircraft missiles. After the test explosion, radiation levels were 20 times normal for about a half-hour over the city of Severodvinsk. Residents in the region quickly bought iodine in anticipation of exposure to radiation. (Read more radiation exposure stories.)