Two people died while participating in a sweat lodge ceremony in Sedona, Arizona, on Thursday. Nineteen others were hospitalized after the two-hour ceremony at the Angel Valley Retreat. Police said self-help author James Arthur Ray was holding a five-day "Spiritual Warrior Retreat," in which his customers sat in a dome-like structure covered with tarps and blankets and filled with steam from hot rocks for hours. When people began to fall ill, emergency responders sent a hazardous-materials team to test for carbon monoxide and other contaminants, but nothing abnormal was found. Authorities are checking to see if the attendees had any pre-existing medical conditions. The county sheriff's office said the deaths and injuries were unusual.