HENDERSON, Nev. » Chelsea Ake-Salvacion felt she was on health care’s cutting edge, working at a cryotherapy center in this Las Vegas suburb that promised to help clients burn calories, reduce pain, strengthen immune systems and halt aging by embedding them in freezing tanks for a few minutes at a time.

In her off hours, she engaged in the practice, and dreamed of opening her own cryotherapy center once she had learned the ropes.

But last week, Ake-Salvacion, 24, was found dead in one of the tanks, discovered by her colleague and friend Elise Iverson. After working an evening shift on Oct. 19 at the Rejuvenice spa here, which offers two forms of deep-freeze therapy in tanks that can reach temperatures of minus 240 degrees Fahrenheit, she had stayed to give herself a cryotherapy session. She was found the next day.

A local coroner’s office said the cause of death had not yet been determined. But Ake-Salvacion’s uncle said the coroner had told him his niece’s body was found "rock-hard solid."

"Something went wrong," said the uncle, Albert Ake, 48. "What she told me is that there is nothing dangerous about doing this. That the only thing that could happen is you’re there a little too long and you get frost nip on your fingers."

The death raised questions about safety in the growing industry of cryotherapy, which is practiced by star athletes and celebrities but is rarely studied and not regulated by any one body. Today, there are cryotherapy centers in New York, Chicago, Los Angeles and elsewhere, though doctors do not agree on its benefits.

In a statement, the owners of the center where Ake-Salvacion died — a two-store chain called Rejuvenice — said that they were "devastated by this accident," and that they were "voluntarily scrutinizing each and every one of our internal procedures to ensure nothing like this ever happens again." The company’s website says that its chambers are "equipped with numerous safety features" and that doors are never locked, allowing clients to exit at any time.

On Monday, a week after the accident, it seemed like business as usual at the Henderson store, a narrow storefront on a corner of a busy street. There are two forms of cryotherapy offered: a one-person cryochamber, which requires the client to wear earmuffs, a mask, gloves, slippers, socks and underwear; and a three-person cryosauna, which does not require the mask or earmuffs.

Cost is based on treatment and need, and the center offers a deal through Groupon, said Hailey Cap, office manager of Rejuvenice. Cap, who said she had known Ake-Salvacion for three years, said that she and other workers at the spa would often use the cryochambers, but never alone.

"We always had someone with us," Cap said.

Ake-Salvacion had moved from Hawaii to Las Vegas in recent years with her boyfriend. When her boyfriend returned to Hawaii, Ake-Salvacion stayed in Nevada, eager to excel at her new job as a manager at the spa, said Ake, her uncle. "She loved that work," he said.

On Monday, Oct. 19, Ake-Salvacion was working a closing shift. About 7:30 p.m. she sent a text message to her boyfriend, telling him that her body was aching and that she was going to hop in one of the tanks for a bit. "That was the last she texted him," Ake said. The coroner’s office told Ake that his niece died just minutes after getting into the chamber.

Ake-Salvacion used to work out at a gym across the street from Rejuvenice, Cap said. "She was working out a lot," Cap said. "She would post her workouts on Instagram."

Cryotherapy is billed as being excellent for muscle pain. "She must have been really sore," Cap said. "I don’t know why she would go in there alone. We don’t do that." One reason people do not try it solo, Cap said, is that the nitrous gas used to chill the air can be debilitating.

The Las Vegas Metropolitan Police Department, which responded to the incident, would not release an incident report, but in an interview a spokesman, Jesse Roybal, said that it did not appear a crime had been committed and that the case remained open. "It doesn’t appear to be suspicious in nature," he said.

The Nevada Occupational Safety and Health Administration was called to the scene, but OSHA officials decided not to open their own investigation. "Due to the fact that the employee was using the chamber for personal use, outside of business hours, OSHA does not have jurisdiction," said a spokeswoman, Teri Williams.

Rejuvenice’s cryotherapy centers allow clients to spend a few minutes inside chambers full of air at below freezing temperatures. Last Tuesday morning, Iverson, the friend and colleague, arrived for her shift and found Ake-Salvacion dead.

"Cryotherapy is safe treatment, it’s definitely safe, but it’s not be used alone," Iverson said. "It was misused."

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