An investigation is underway after the employee of a cryotherapy “rejuvenation” company froze to death in the machine that can expose the body to temperatures of minus 240 degrees Fahrenheit.

Officials have told the family of Chelsea Ake-Salvacion, 24, of Las Vegas, that she would have died in seconds. It appears her body may have spent up to ten hours in the machine.

“I do know that she was alone closing the shop up, and then did go into the machine and apparently did not turn off,” Shae-Lynn Bee, Ms Ake-Salvacion’s friend, told KSNV News.

“It’s very frustrating to know because you know there are no cameras in there. Basically, the only person that does know what happened is Chelsea.”

Ms Ake-Salvacion, who worked at the Rejuvenice salon in Las Vegas, had apparently been a believer in the benefits of the treatment, which is often used by athletes to help their bodies recover quickly after training or though games.

The treatment is often followed by a facial and moisturiser treatment.

“We like to do the cryofacial afterward because it helps seal everything in,” Ms Ake-Salvacion had recently told the Las Vegas Review-Journal.

Medical examiners told her family she died in “seconds” on Oct. 20 after she entered the machine alone, and her family says she “froze to death.”

Cryotherapy is described as the use of low temperatures for “medical therapy,” the centre’s website said. It’s been used as “early as the seventeenth century.”

Ms Ake-Salvacion's family disagrees with TV news reports that said the woman's death was the result of operator error. She was an aesthetician and a chamber operator, her uncle said

On October 19, Ms Ake-Salvacion worked as the center's night supervisor. She was seen on video cameras closing the business, he said. She was last seen on video walking to the back of the centre.