Four Americans who have been wrongfully detained in Iran have been released from prison and are now under house arrest, a lawyer for one of the prisoners told CNN on Thursday, a sign that they may soon be freed from years of imprisonment.

"The move by Iran of the American hostages from Evin Prison to an expected house arrest is an important development," said Jared Genser, pro bono counsel to Siamak Namazi, one of those released. "While I hope this will be the first step to their ultimate release, this is at best the beginning of the end and nothing more."

The Americans -- Namazi, Emad Sharghi, Morad Tahbaz, and a fourth American who has not been identified publicly -- were moved from Tehran's notorious Evin Prison, and are anticipated to be held at a hotel under guard by Iranian officials.

The Biden administration has been engaged in negotiations to try to secure their release from Iran, a country with which it does not have diplomatic relations.

Genser strongly cautioned against being overly optimistic about freedom for the Americans until they are actually out of Iran. "There are simply no guarantees about what happens from here," he said.

CNN has reached out to the US State Department and National Security Council for comment.

This is a breaking story and will be updated.