(CNN) -- An investigation into the deaths of two people who spent up to two hours inside a "sweat lodge" at an Arizona retreat last week has been elevated from an accidental death investigation to a homicide inquiry, Yavapai County Sheriff Steve Waugh told reporters Thursday.
Self-help author James Arthur Ray has hired investigators to investigate two deaths at an Arizona sweat lodge.
Authorities said James Shore, 40, of Milwaukee, Wisconsin, and Kirby Brown, 38, of Westtown, New York, died Friday at the Angel Valley Resort after spending up to two hours in the sauna-like sweat lodge. Nineteen others were treated for injuries. One person remained hospitalized Thursday in critical condition, Waugh said.
The dead and injured were attending a program by self-help author James Arthur Ray, authorities said.
A search warrant was executed Wednesday at the James Ray International offices in Carlsbad, California, the sheriff said. Authorities were attempting to determine whether documents exist on how to construct sweat lodges and on their proper use, as well as documents showing whether participants were advised of the risks of sweat lodges either before or during the program. They also were searching for rosters from past events, Waugh said.
Police would not say what, if anything, was found in executing the search warrant. Watch what goes on inside the 'sweat lodge' »
Asked why the deaths have been classified as homicides and the investigation upgraded, Waugh said, "We believe there are indications that it was not accidental, and ... we feel that there should be some culpability on some individuals."
Those individuals could include Ray and possibly others, he said.
A spokesman for Ray said authorities should be focusing on the investigation rather than talking to reporters. "The Sheriff's Department is trying this case in the media," said Howard Bragman, noting that Thursday's news conference was the sheriff's second this week.
"There were no additional facts presented today; there were implications. I find words like 'homicide' -- when they don't have all the facts -- inflammatory and inappropriate at this time, and I think they're purposely inflammatory. ... Let's show as much zeal with the investigation and getting to the facts as they have in trying to tar my client," Bragman said.
The sweat lodge was meant to be a "spiritual awakening" exercise for the participants in the "Spiritual Warrior" program, Waugh said.
A sweat lodge is a dome-like structure covered with tarps and blankets. Hot rocks and water are used to create steam in the enclosed environment.
The owners of the resort built the sweat lodge, Waugh said, under Ray's direction. A nurse on Ray's staff was present during the event, police have said.
At least one of those who died was in the back of the structure, Waugh said. Ray was positioned near its door. There were no seats, he said; participants either sat or lay on the floor.
On Tuesday, Ray said he has hired his own investigators to determine what happened at his Arizona retreat, located in a secluded valley 20 minutes from Sedona. "I have no idea what happened. We'll figure it out," Ray said. "I've lost people I love and really care about."
Ray is the author of the best-selling book "Harmonic Wealth: The Secret of Attracting the Life You Want." Ray, described on his Web site as a "personal success strategist," has appeared on CNN's "Larry King Live" and the "Oprah Winfrey Show," and is featured in the self-empowerment film "The Secret."
The use of sweat lodges for spiritual and physical cleansing is a part of several Native American tribes' cultures.
A traditional Native American sweat lodge is a small dome-like structure made of willow branches carefully tied together and covered in canvas. Rocks are heated in a nearby fire pit and placed inside the lodge, and water is poured over them to create steam.