More details have slowly begun to emerge of a tentative deal that would see the United States and Iran engage in a prisoner swap in exchange for giving the Iranian government access to billions of dollars in frozen funds.

News of the agreement first broke on Thursday as US news outlets reported that four American detainees had been transferred from Tehran’s notorious Evin prison to house arrest in a hotel. A fifth prisoner had been released earlier.

Both US and Iranian officials later confirmed the first steps of the agreement but have given differing accounts of what it involves.