Two people who paid up to $9,000 to attend a retreat for holistic treatments and spiritual in a natural setting, died while in a sauna-like room.

According to Arizona police, 50 people were inside a so-called “sweatbox” at Angel Valley resort for up to two hours and 19 people became ill and two, a middle-aged man and woman, died.

The 70-acre resort, which is 115 miles north of Phoenix, offers a wide range of treatments from massage to colon cleansing, healing carried out by harnessing the consciousness of a dolphin, or “vortex experiences” in which participants “experience our human energy system interacting with the earth.”

Authorities said that during the sweatbox experience, the tent was gradually filled with steam generated by pouring water on to fire-heated rocks brought inside the dome.

Homicide detectives were among investigators combing the site, with tests being carried on air inside the dome and searches of buildings at the retreat.