Tehran did its utmost to conceal the mystery blast which last week struck the heavy water reactor under construction at Arak in western Iran. It is revealed here for the first time by DEBKAfile’s intelligence and Iranian sources. The explosion, whether accidental or not, will delay for a second time the reactor’s first test with real fuel. Tehran informed the International Atomic Energy Agency in August of a previous holdup. The cause of the blast and the extent of the damage it caused have not yet been established. According to the partial information initially reaching our sources, it occurred inside...