Reports from Tehran say the public prosecutor has launched the investigation of peace activist Ali Shakeri.
Iran has charged two U.S.-Iranian scholars -- Haleh Esfandiari and Kian Tajbakhsh -- with spying. A third, Radio Farda reporter Parnaz Azima, has been charged with "antirevolutionary" activities.
The U.S. State Department has expressed dismay about the detention and harassment of U.S.-Iranian citizens for what it calls "groundless charges."
On June 5, the U.S. House of Representatives passed a nonbinding resolution calling for the immediate release of all four Iranian-Americans.
(with material from Reuters)
