The Tasnim, ISNA and Mehr news agencies all carried the same photograph on their Telegram accounts of Asgari, wearing a face mask against the coronavirus, being reunited with his family.
A US court had in November cleared Asgari of charges of stealing trade secrets in 2016 while he was on an academic visit to Ohio from Tehran's Sharif University of Technology.
The 59-year-old told British newspaper The Guardian in March that the US Immigration and Customs Enforcement (ICE) agency was holding him at a Louisiana detention centre without basic sanitation and refusing to let him return to Iran despite his exoneration.
Iranian foreign ministry spokesman Abbas Mousavi denied Tuesday that Asgari's release was part of a prisoner exchange and said "he was freed after being exonerated", adding that his return was delayed because he was infected with COVID-19.
"Mr. Asgari was stranded in America for a while because of (being infected with) the coronavirus and the situation with flights," he said.
The State Department has yet to respond to an AFP request to comment on his release.
However Ken Cuccinelli, the acting deputy secretary of US homeland security, said on Twitter that the US had been "trying to deport" Asgari since last year but that it had been "stalled every step of the way by the Iranian government".--AFP