At least nine workers have been killed in an explosion at a mine in northern Russia, news agencies said. State-run RIA-Novosti cited an unidentified law enforcement official as saying three other people were still missing and six others were injured by the blast Thursday at a mine in the Murmansk region. Interfax cited an unidentified emergency official as saying 12 people were killed and four injured. According to RIA-Novosti, the mine belongs to a major company that produces a fertilizer component. It cited the law enforcement official as saying the blast occurred while workers were conducting controlled explosions at the mine.