Washington Post: Iranian nuclear engineer Mohsen Fakhrizadeh lectures weekly on physics at Tehran's Imam Hossein University. Yet for more than a decade, according to documents attracting interest among Western governments, he also ran secret programs aimed at acquiring sensitive nuclear technology for his government.

Experts at the International Atomic Energy Agency (IAEA) have repeatedly invited Fakhrizadeh to tea and a chat about Iran's nuclear work. But for two years, the government in Tehran has barred any contact with the scientist, who U.S. officials say recently moved to a new lab in a heavily guarded compound also off-limits to U.N. inspectors.