Iran released four prisoners Saturday, including jailed Washington Post correspondent Jason Rezaian.

All four of those released are Iranian-American dual nationals, including Rezaian. He has had been in Iranian custody since July 2014. Also freed were former U.S. Marine Amir Hekmati, Christian pastor Saeed Abedini and a fourth American-Iranian national, Nosratollah Khosravi-Roodsari.

"Through a diplomatic channel that was established with the focus of getting our detained U.S. citizens home, we can confirm Iran has released from imprisonment four Americans detained in Iran" the State Department said in a statement Saturday. "Iran has also committed to continue cooperating with the United States to determine the whereabouts of Robert Levinson."

Levinson, an American private investigator and former Federal Bureau of Investigation agent, went missing in March 2007 while on an investigative trip to Iran. U.S. officials have suggested they doubt he is still alive.

The releases came in exchange for the release of Iranians held in the United States.

"We offered clemency to seven Iranians, six of whom are dual U.S.-Iranian citizens, who had been convicted or are pending trial in the United States," the State Department said. "The United States also removed any Interpol red notices and dismissed any charges against 14 Iranians for whom it was assessed that extradition requests were unlikely to be successful."

Rezaian was convicted of espionage against the Iranian state and "propaganda against the establishment" in October 2015. In November 2015 he was sentenced to a prison term of undisclosed length.

The prisoner release caps a harrowing week for U.S.-Iran relations. Iran temporarily captured of 10 U.S. sailors Tuesday. The Iranian nuclear deal is set to be formally put into place in the coming days.

The exchange was announced as the International Atomic Energy Agency prepared to certify that Iran had met all commitments under a landmark nuclear deal with six world powers. Secretary of State John Kerry was headed to a meeting in Vienna with Iranian Foreign Minister Mohammad Javad Zarif and other officials involved in the accord as the news occurred.

Certification by the IAEA, expected Saturday, would allow Iran to recoup more than $100 billion in assets frozen overseas. The deal also gives Iran relief from oil, trade and financial sanctions.

Hekmati's lawyer, Mahmoud Alizadeh Tabatabaei, said Hekmati called him earlier Saturday from prison, according to the Associated Press.

"He told me that judiciary officials have called for a meeting with him. But I've not been formally informed if he is free now," Tabatabaei said.

Ted Cruz, a prominent Iran nuclear deal critic, seemingly lauded a positive byproduct of the deal: more open communication with the Iranians. Cruz highlighted the release of Saeed.

"Praise God! Surely bad parts of Obama's latest deal, but prayers of thanksgiving that Pastor Saeed is coming home," Cruz tweeted.