The Islamic Republic Foreign Minister, Mohammad Javad Zarif, has accused the United States of taking "several" Iranian scientists hostage.

In a tweet on Friday, March 27, Zarif maintained, "The U.S. even refuses medical furlough — amid #covid19 — for innocent men jailed in horrific facilities. Release our men."

Referring to a report by The Guardian newspaper about an Iranian science professor, Dr. Sirous Asgari, who it said was still being held after being acquitted in November on U.S. federal charges of stealing trade secrets, Zarif tweeted, "The U.S. has taken several Iranian scientists hostage—without charge or on spurious sanctions charges—& not releasing them; even when its OWN courts reject the absurd charges." Zarif did not name any other detainee.

An Iranian scientist who was found not guilty in a U.S. sanctions trial but remains jailed by U.S. Immigration told Guardian on Thursday the conditions in detention were filthy and overcrowded – and officials were doing little to prevent a deadly coronavirus outbreak.

Asgari, a materials science and engineering professor, was charged with stealing trade secrets related to his academic work with a university in Ohio.

Asgari has also told The Guardian that he was suffering from respiratory complications, and worried about contracting the deadly novel coronavirus. He has insisted that he wants to return to Iran.

The U.S. has called on Iran to release American dual nationals held in the Islamic Republic jails.

On March 19, Tehran agreed to grant furlough to an American citizen, Michael White, who has been kept behind bars.

Detained by Iran for over 600 days on spurious charges, White has been hospitalized with symptoms consistent with the novel coronavirus, according to his family's spokesperson.

An American navy veteran, Michael White, 48, has not yet been tested positive, but there are deep concerns over his health as Iran struggles to contain coronavirus outbreak.

"His situation is urgent," family spokesperson, Jonathan Franks, said in a statement Wednesday night. "It is in everyone's interest during this health crisis to facilitate Michael's immediate medical evacuation."

Referring to White's release, U.S. Special Representative for Iran Affairs, Brian Hook, said on March 19, "We hope this is the first step. Right now, it is just a medical furlough."

Furthermore, Hook called upon the Islamic Republic leaders to release all dual Iranian-American citizens, including renowned environmentalist, Morad Tahbaz and businessman, Siamak Namazi.