A Nov. 6, 2013, photo shows Jason Rezaian, a Washington Post reporter, at the newspaper in Washington. The Iranian government has not said why the reporter was detained nearly two months ago. (Zoeann Murphy/AP)

A senior Iranian official said Wednesday that Jason Rezaian, a Washington Post reporter detained in Tehran nearly two months ago, is being interrogated on unspecified charges by judicial authorities.

“He is facing interrogation in Iran for what he has done as an Iranian citizen,” Foreign Minister Mohammad Javad Zarif said in an interview with NPR.

Zarif did not say why Rezaian, a dual American and Iranian citizen, was arrested or what charges he may be facing. He said Iran’s judiciary has “no obligation to explain” any charges to the United States.

“His lawyers know. He knows his charge. I’m not supposed to know, but he knows his charge,” Zarif said, adding that the judiciary operates independently.

The Iranian government has said little about Rezaian’s case since he was detained July 22, and according to his family, he has not had access to a lawyer. His wife, Iranian journalist Yeganeh Salehi, and two others, a photojournalist and her husband, were arrested at the same time.

A picture made available on 25 July 2014 shows the Washington Post Iranian-American journalist Jason Rezaian, right, and his Iranian wife Yeganeh Salehi, who works for the UAE newspaper National. (Stringer/EPA)

Only Rezaian and Salehi are still being held. The other two, whom The Post has not named at the request of their families, have been released.

Zarif, who is in New York for negotiations over Iran’s nuclear program, said he knows Rezaian personally and hopes for his release.

“I know him to be a fair reporter, so I had hoped all along that his detention would be short, and I continued to try to make it shorter, [rather] than longer,” he told NPR. “But the point that needs to be made is that an Iranian citizen is being held by Iranian authorities on suspicions dealing with Iranian law.”

Iranian President Hassan Rouhani and other world leaders are gathering next week in New York for the United Nations General Assembly. Zarif is also participating in negotiations over Iran’s nuclear program with the United States and five other major powers.

The State Department has called on Iran to release Rezaian and his wife, and The Post has said it does not know what charges Rezaian might be facing.

“The two have been held for more than eight weeks without explanation or charges,” Douglas Jehl, The Post’s foreign editor, said in a statement. “The two are fully accredited journalists, and we remain mystified by their detention and deeply concerned about their welfare.”

Martin Baron, executive editor of The Post, and Rezaian’s family have said that Rezaian’s health is of particular concern. He has high blood pressure, which requires him to take medication daily.

“The authorities ... have conducted a two-month-long investigation from which they have produced no evidence of wrongdoing by either Jason or Yeganeh,” Rezaian’s older brother, Ali, said in a statement. “Neither I nor my mother have been permitted any communication with Jason. We remain concerned about their health and implore the Iranian authorities to release them in compliance with Iran’s existing laws and constitution.”