The authorities say that at any one time 55 to 65 people were packed for a two-hour period into a 415-square foot structure that was 53 inches high at the center and 30 inches high on the perimeter. Mr. Ray’s employees built the wood-frame lodge, which was wrapped in blankets and plastic tarps. Hot rocks were brought into the lodge and doused with water. Mr. Ray, who conducted the ceremony, left the area on Thursday after declining to give a statement to the police.

Sheriff Steve Waugh of Yavapai County said a death investigation would continue for several weeks. Mr. Ray, the Angel Valley owners, Michael and Amayra Hamilton, and all the participants are part of the investigation, the sheriff said. The results from autopsies that were conducted Friday have not been released and results from toxicology tests are not expected for several weeks.

Dr. Carroll, who is partly of Mescalero Apache descent, said the Angel Valley sweat lodge was the “best example I have seen, sadly, in a long time of why it is extremely dangerous to conduct sweat lodge ceremonies without proper training.”

Katherine Lash, a co-owner of Spiritquest Retreat in Sedona and a veteran of more than 100 sweat lodge ceremonies, said she had never heard of a sweat being conducted with as many people as were involved in the Angel Valley event. “In my experience it has been very rare to have more than 20 people,” she said.

Limiting the number of people inside a sweat lodge is critical because the person leading the event is supposed to carefully monitor the mental and physical condition of each participant, experts said.

“It’s important to know who is responsible for your spiritual and physical safety in that lodge,” said Vernon Foster, a member of the Klamath-Modoc tribe who regularly leads ceremonial sweat lodge events in central Arizona.

Mr. Foster said native people would use only natural materials in the construction of a sweat lodge. “We would never use plastic to cover our lodges,” he said. “The lodge has to breathe, that steam has to go someplace.”