Iran said on Tuesday it has new evidence linked with national security charges against US-Iranian Haleh Esfandiari, and it is continuing to probe into the detained scholar's case.
"Some new evidence has been found and the inspector is examining it. As it is a new investigation it should go on," judiciary spokesman Alireza Jamshidi told reporters.
"This evidence is linked with the previously mentioned charges of acting against internal security."
Prosecutors have accused Esfandiari, who has been behind bars since May, and two other detained US-Iranians of espionage and acting against national security.
Esfandiari, 67, heads the Middle East programme at the Washington-based Woodrow Wilson International Center for Scholars. She was arrested after returning to Iran late last year to visit her ailing 93-year-old mother.
Iranian Nobel peace laureate Shirin Ebadi, who was appointed Esfandiari's lawyer by her family, has complained she had been denied access to her client and that the judiciary refused her request to release the scholar on bail.
A fourth US-Iranian, journalist Parnaz Azima, has been accused of similar charges and is unable to leave the Islamic republic after having had her passport confiscated. But she is not being held in jail.
The United States has repeatedly demanded that Iran release all the US-Iranian detainees but Tehran -- which does not recognise dual nationality -- has bluntly told Washington the affair is none of its business.