(Bloomberg) Jake Rudnitsky and Stepan Kravchenko August 12 2019 5:06 AM The failed missile test that ended in an explosion killing five atomic scientists last week on Russias White Sea involved a small nuclear power source according to a top official at the institute where they worked. The men tragically died while testing a new special device" Alexei Likhachev the chief executive officer of state nuclear monopoly Rosatom said at their funeral Monday in Sarov a high-security city devoted to atomic research less than 400 kilometers (250 miles) east of Moscow where the institute is based. The part of the Russian Federal Nuclear Center that employed them is developing small-scale power sources that use radioactive materials including fissile and radioisotope materials" for the Defense Ministry and civilian uses Vyacheslav Soloviev scientific director of the institute said in a video shown by local TV. Were analyzing the whole chain of events to assess both the scale of the accident and to understand its causes" he said. The blast occurred Aug. 8 during a test of a missile engine that used isotope power sources" on an offshore platform in the Arkhangelsk region close to the Arctic Circle Rosatom said over the weekend. The Defense Ministry initially reported two were killed in the accident which it said involved testing of a liquid-fueled missile engine. The ministry didnt mention the nuclear element.