When $6 billion of unfrozen Iranian funds are wired to banks in Qatar as early as next week, it will trigger a carefully choreographed sequence that will see as many as five detained U.S. dual nationals leave Iran and a similar number of Iranian prisoners held in the U.S. fly home, according to eight Iranian and other sources familiar with the negotiations who spoke to Reuters.

As a first step, Iran on Aug. 10 released four U.S. citizens from Tehran’s Evin prison into house arrest, where they joined a fifth, who was already under house arrest. Later that day U.S. Secretary of State Antony Blinken called the move the first step of a process that would lead to their return home.

They include businessmen Siamak Namazi, 51, and Emad Sharqi, 59, as well as environmentalist Morad Tahbaz, 67, who also holds British nationality, the U.S. administration has said. The Tahbaz and Shargi families did not respond to requests for comment. A lawyer for the Namazi family declined to comment.

The identities of the fourth and fifth Americans, one of whom according to two sources is a woman, have not been disclosed. Reuters couldn’t establish which Iranian prisoners, in turn, would be swapped by the U.S.