(CNN) -- Peruvian authorities say they have arrested four members of a gang that specialized in selling to European labs fat obtained from dead humans.
Officials are investigating the disappearance of at least 60 people they believe were killed by gang members in two mountainous states in central Peru, lead prosecutor Jorge Sanz Quiroz said Friday.
The four suspects have been charged with murder in the September slaying of a Peruvian man, the prosecutor said.
"They killed to obtain human fat because there were European laboratories that would pay them," Sanz Quiroz said.
The suspects told authorities they were paid $15,000 for a liter (about 1 quart) of human fat.
Officials did not disclose what possible use laboratories could have for the human fat, but fat can be a component of cosmetics and is used in reconstructive or cosmetic surgery. The use of human fat for any purpose is extremely rare, however, physicians say.
Other suspects, including the Peruvian ringleader, have eluded capture, Sanz Quiroz said.
Authorities have the names of two Italian suspects who are being sought by Interpol, the 188-nation worldwide police agency, the prosecutor said. He declined to reveal their identities.
Sanz Quiroz acknowledged the uniqueness of the allegations.
"We are not making this up," he said. "They have confessed to this. That's what's coming out now."
One of the suspects told officials he had been committing the murders for five years.
According to a criminal complaint Sanz Quiroz filed November 18, officials discovered on September 22 a small container containing a fat-like substance that had been stored at the Bella Durmiente bus station in Lima, Peru's capital.
On November 3, the complaint says, suspect Serapio Marcos Veramendi Principe was arrested after he retrieved three bottles from the Estrella Polar bus station. The bottles contained a substance authorities believe is human fat, the complaint says. Lab tests are being performed to determine what the substance is.
Authorities identified the three other suspects as Elmer Segundo Castillejos Aguero, Hilario Cudena Simon and Enedina Estela Claudio. The suspects identified each other for police in photo lineups, the complaint says.
In addition to murder, Veramendi Principe and Castillejos Aguero face weapons charges. Castillejos Aguero, Veramendi Principe and Estela Claudio also face drug charges, authorities said.
They are accused in the September 16 killing of Abel Matos Aranda, the criminal complaint says. Authorities believe the substance found at the bus stations is body fat obtained from Matos Aranda.
Officials unearthed a partially buried male body November 13 in Huanuco state. They believe it was Matos Aranda.
Sanz Quiroz referred to the suspects as "brujos," the Spanish word for witches. He noted that the suspects are part of an Andean mountain culture that believes bodies can be used to ward off evil and prevent disasters.
For example, he said, bodies are often buried at the entrances to mine shafts and bridges in the belief they will keep the structures from collapsing.
Authorities are calling the suspects "pishtacos," which are Andean mythological creatures.
In his 1996 book "Death in the Andes," Peruvian author Mario Vargas Llosa mentions pishtacos extensively, saying they are half-white ghouls who live in caves, lurk along dark isolated roads and suck the fat out of anyone careless enough to travel Andean roads at night. Andean myth holds that the fat is used to make soaps, lubricants, healing potions and cosmetic creams.
Until the arrests, few believed that anything resembling pishtacos existed.
"It's an Andean myth that we've now been able to prove," said Miguel Jimenez Torres, a spokesman for the prosecutor's office.
Some physicians say human fat is used in some medical procedures, but a few products were taken off the market because they were considered unsafe.
The longevity of implants that use human tissue often is not as good, said Atlanta cosmetic surgeon Harold Brody. Nor is there any advantage, he said, to using human fat in cosmetic creams or lotions.
"They're a little behind the times," Brody said. "It makes a great moisturizer, but it has no advantages over good moisturizers that don't use human fat."
New York dermatologist Barry Goldman said he had never heard of human fat being sold on the black market.
"The idea that anybody would use an injectable where you didn't know where it came from would be laughable if it weren't unethical and potentially dangerous," he said.
Still, the notion of black market human fat seemed possible to him.
"They steal kidneys, so why not this?" he asked. "It is sick, but in the Holocaust they did use skin for lamps."