An Iranian scientist who had been detained in the United States has landed in his homeland amid denials from both countries that his release is part of a prisoner swap.

Sirous Asgari, a materials science professor at Tehran's Sharif University of Technology, arrived in Iran on June 3, the semiofficial ISNA news agency reported.

The 59-year-old Asgari was charged in 2016 with attempting to steal trade secrets from a research project being carried out by Case Western Reserve University in Ohio. He denied the charge and was acquitted in November after a U.S. judge tossed out the case filed by the prosecutors.

The United States and Iran conducted a swap in December, when Chinese-American researcher Xiyue Wang and Iranian scientist Massud Soleimani were freed.

SEE ALSO: Amid Tensions, Iran And United States Swap Detainees

Asgari's return to Iran led to speculation that he could be part of another prisoner swap.

But Iranian Foreign Ministry spokesman Abbas Musavi said that talk of a prisoner exchange was 'groundless' because Asgari was 'released on the basis of being acquitted.'

State Department spokeswoman Morgan Ortagus later said 'Asgari is not and has never been a participant in any prisoner swap with Iran.'

Several other U.S. citizens are currently imprisoned in Iran or out on bail, including Navy veteran Michael White, who was temporarily released from prison in March on medical grounds amid the coronavirus pandemic.

White was arrested in 2018 and sentenced to 13 years in prison for allegedly insulting Iranian Supreme Leader Ayatollah Ali Khamenei and posting private information online.

Relations between Washington and Tehran have become increasingly hostile since 2018, when President Donald Trump withdrew the United States from a landmark nuclear deal between Iran and world powers.

With reporting by ISNA

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