Princeton University says a grad student imprisoned in Iran was working on his doctorate there.

FOX's Rachel Sutherland reports from Washington:

The University says it is "very distressed" by Xiyue Wang's imprisonment in Iran. The 37-year-old doctoral student was convicted of spying and sentenced to 10 years.

Wang was arrested last summer while working on his dissertation in Iran. The school says he was doing research on Eurasian history. One of his professors, Steven Kolkin, told the AP that Wang is innocent of all charges.

The U.S. State Department has called on Tehran to "release all U.S. citizens unjustly detained in Iran."

In Washington, Rachel Sutherland, FOX News.

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