ROME — Last year when aid agencies in Italy shared the grim news that as many as 10,000 migrants and refugees, many under the age of 18, had disappeared without a trace, most people assumed they had just escaped to other parts of Europe.

Now, it would seem, we know what really happened to some of them.

Atta Wehabrebi, an Eritrean human trafficker who is the first migrant turncoat in the Italian court system, and who is now part of Italy’s witness protection program, told investigators that migrants and refugees who can’t afford to pay their traffickers are consistently sold for their organs to an Egyptian crime ring for €15,000 to cover their travel costs. Over the weekend, 38 mostly Eritrean and Ethiopians were arrested in connection with the illicit activity. Of those, 23 are in custody and 15 remain at large.

The migrants and refugees, many of whom are women and children, are generally sacrificed in the harvesting process, especially when multiple organs are taken from the same victim, according to police reports citing Wehabrebi published in the Italian press. Wehabrebi says some cash-strapped migrants are given an opportunity to sell their organs in exchange for their trafficking transport costs, but the majority are either taken back to Egypt or killed in Italy. The harvested organs are then sold on a lucrative black market to wealthy Europeans and Russians, Wehabrebi told prosecutors in Sicily.

The trade in illegal organ transplants is on the rise across the world, aimed at meeting demand from wealthy people who don’t want to wait on long lists for available donors, according to the Global Initiative to Fight Human Trafficking. “Organs which are commonly traded are kidneys, liver, and the like,” the organization says. “Any organ which can be removed and used could be the subject of such illegal trade.”

The victim donors’ bodies are then dumped at sea or buried in deep ditches in Sicily, according to Wehabrebi. “The Egyptians have all the equipment to harvest the organs,” he said, according to police reports made public after the arrests this weekend. “They even transport the organs in special insulated bags.”

In April, the bodies of nine Somalis washed up on the beaches of Alexandria, with their bodies cut open and vital organs missing.

Wehabrebi began cooperating with investigators shortly after his arrest in 2014. In a plea arrangement, he was sentenced to five years in prison for his part in a deadly shipwreck that killed more than 300 people off the coast of Lampedusa that year. He said that he cooperated because of the “guilt and anguish” he had suffered seeing many of his fellow countrymen and women perish at sea.

Wehabrebi’s leads have led to a number of discoveries, including an illegal hawala payment system that was run out of a small five-and-dime perfume shop near Rome’s Termini station with connections to agents in Dubai and Israel. Investigators set up hidden cameras in the shop and were able to uncover the intricate financial system for traffickers.

On Wednesdays and Saturdays, agents from Ethiopia apparently would deliver massive sums of dollars and euros that had been received illegally. In a manner typical of this ancient informal means of transferring, or laundering, money, those payments were logged in a simple appointment book kept among the bottles of cheap shampoo and toothpaste.

The cash represented payments by various refugees and migrants who had escaped the official reception centers, according to Renato Cortese, the lead investigator on the Sicilian investigative team that led the sting operation.

Most refugees and migrants pay all or part of their sea travel in cash in North Africa, but are required to pay the rest for further travel into Europe when they arrive in Italy.

A similar shop was found in Palermo, Sicily, where migrants often gather to find work in the black market agriculture and illegal drug sectors.

Officers in Rome confiscated €526,000 and $25,000 dollars in cash along with the log book from the Rome store.

Wehabrebi says that refugees and migrants whose families failed to pay the debts back in Africa or across Europe were sought out for their organs and never seen again.

The shop owner and his wife were among those arrested over the weekend.

Wehabrebi also told investigators that the deaths that make the headlines are only a small part of those who die at sea. “Eight out of 10 families in Eritrea have lost someone on the journey,” he told police, according to press reports.

More than 230,000 people have arrived in Europe by sea in 2016 so far, according to the United Nations Refugee Agency. Nearly 3,000 people are known to have died trying to make the journey. If Wehabrebi’s confessions are true, the death toll could be many times higher.