Tajbakhsh, an Iranian American who holds a doctorate in urban planning from Columbia University, was arrested by Iranian authorities in May 2007, charged with spying and then released after more than four months in Tehran’s Evin prison.
It was not clear why Tajbakhsh was detained last week.
Iran has sought to crush demonstrations after its disputed June 12 presidential election, which defeated candidate Mirhossein Mousavi says was rigged in favor of hard-line President Mahmoud Ahmadinejad.
