An explosion has hit the Sverdlov defense plant in Russia’s Nizhny Novgorod region, killing three and leaving another three missing, TASS reported Friday, citing a regional law enforcement source. An ammonal explosive went off in one of the plant’s workshops, and a technological process disruption is believed to have caused the blast, the source said. A fire broke out after the blast, engulfing an area of 100 square meters, said firefighters who were working at the scene. The blaze has been categorized as a three-alarm level.