A Princeton graduate student was sentenced to 10 years in Iranian prison on Sunday over charges of espionage.

According to a statement issued by Princeton University, Xiyue Wang was arrested nearly a year ago as he was about to leave Iran. He had been conducting scholarly research about the late Qajar dynasty.

“We were very distressed by the charges brought against him in connection with his scholarly activities, and by his subsequent conviction and sentence. His family and the university are distressed at his continued imprisonment and are hopeful that he will be released after his case is heard by the appellate authorities in Tehran,” the statement said.

“In the interim, the university will continue to do everything it can to be supportive of Mr. Wang and his family.”

The court decision comes at a tense time for U.S.-Iranian relations as they have just recently approved a waiver that would expand sanctions relief following the Iranian nuclear deal. Although the White House was expected to approve the waiver, recent tensions between the two countries had called its confirmation into question.

This is not the first time a U.S. citizen has been unexpectedly detained in Iran. The State Department released a statement in April calling for the release of two other U.S. citizens from Iranian captivity. Siamak Namazi and his father, Baquer Namazi, were detained months apart from one another and remain in Tehran’s Evin Prison.

“The United States is deeply concerned about reports of their declining health and well-being in detention. The United States urges Iran to immediately release Siamak and Baquer on humanitarian grounds,” the statement said.

The State Department has also said that an unspecified number of U.S. citizens and foreigners from other countries continue to be held by the Iranian government on “fabricated ­national-security related changes.”