“There is lots of dust, it is very easy to catch colds, and we hurt all over.”

The statement, delivered by a 15-year-old in the Democratic Republic of Congo (DRC), marks the foundation of a new report from Amnesty International. Released this week, it reveals a working situation so terrible for those that mine minerals used in smartphones that it borders on slavery.

Titled “This Is What We Die For,” the report traces the cobalt from lithium batteries that Apple, Sony, and 14 other companies use in their devices to unregulated mines in the DRC. The 88-page account builds on earlier reports that miners in this region risk abuse and death to make just $2/day mining cobalt.

But on top of hazardous, unethical work conditions, it exposes an overlooked fact about the miners themselves: at least 40,000 of them are children. If tech companies are making billions churning out better and faster smartphones, they may be doing it on the backs of African kids.

***

To conduct the report, Amnesty—in partnership with African Resources Watch (Afrewatch)—visited five mining sites in the southern portion of the DRC, from April-May 2015. The country, with a population of at least 67 million, is one of the poorest in the world. In 2014, the World Bank ranked it second to last on the Human Development Index.

But if there is one thing that’s plentiful in the DRC, it’s cobalt. Experts estimate that more than half of the world’s supply comes from that one country alone, with 20 percent of it from what are called “artisanal mines.” For Congolese who are able to tolerate the work, it is plentiful—however it seems rarely, if ever, a choice.

The vast majority of the 100 miners that the researchers interviewed said it was the only job available; one said they had to do in order to eat. Those whose children were working said they couldn’t afford to send them to school. A handful that was able to send their kids to school had to ask their children to work on the weekends.

Artisanal mines, where most work, are smaller, independent mines where an industrial-sized operation is not an option. Without a large corporation behind it, artisanal mines are somewhat of a free-fall. They are not a part of the country’s Mining Code and Regulations, meaning they are often unauthorized and extremely dangerous.

As a result, the workers are subjected to dangerous conditions that include poor ventilation, lack of protective gear, and frequent accidents—many of which prove deadly. But it’s not just adults that are risking their lives. Of the almost 100 mine workers the organization interviewed, 17 of them were children.

Working in high temperatures, rain, and storms, Amnesty found kids as young as 7 carrying sacks of mineral ore heavier than themselves. Many suffered from breathing problems, others from sickness and disease. At least half reported being beaten for not working fast enough. None, it seemed, had a way out.

One former worker, Loic, reported severe back pain from the grueling work he did, beginning at age 9. A 14-year-old told the researchers he hardly left the tunnel he worked in, hundreds of feet below the ground. “[I spent] 24 hours in the tunnels,” he told them. “I arrived in the morning and would leave the following day.” One more, aged 15, said he worked for food. “All the money I earn in the mines I spend on food,” he said. “Because at home we don’t eat.”

Among the potential long-term effects the children can suffer from include joint and bone deformities, respiratory issues, and musculoskeletal injuries. Most complained of excruciating back and hip pain, others of chronic illness. But beyond physical risks are less visible dangers. Chronic exposure to cobalt can be fatal, resulting in a condition called “hard metal lung disease.”

Despite the prevalence of studies confirming this, Amnesty found no evidence of protective equipment at the mines—no gloves, masks, or even work clothes. The workers had never been provided safety equipment nor given directions on what to do in a crisis. Without any sort of armor against the hazardous conditions, death is common.

While Amnesty could not find an official death toll, an independent radio station in the DRC reports at least five to six accidents a month—some of which kill dozens at a time. According to their reports, 15 miners died in a fire near Kasulo on Dec. 26, 2014; on Sept. 13, 2015, 14 more were killed after a tunnel collapsed in Mabaya.

Many miners told them that the numbers are much higher but that many of the bodies, due to the poor structure of the tunnels, are never recovered. “There are many accidents. Many tunnels collapse,” said 32-year-old artisanal miner Emmanuel. “The bodies are still there.”

***

After witnessing the conditions at the mines, Amnesty and Afrewatch followed the route of the cobalt, which brought them to a large corporation called Congo Dongfang Mining International (CDM). CDM is a subsidiary of the China-based company Huayou Cobalt, which supplies batteries to the most prestigious tech companies—including Apple, Sony, Samsung, and Dell.

The researchers reached out to all 16 companies connected with Huayou Cobalt, and got a variety of replies. The report says just one of the 16 “admitted the connection,” while four others said they were “unable to say.” Five denied sourcing from Huayou (despite documents proving otherwise), and six said they were “launching investigations.”

Apple, who has been criticized for labor practices in the past, said it was “currently evaluating dozens of different materials, including cobalt, in order to identify labor and environmental risks as well as opportunities for Apple to bring about effective, scalable and sustainable change.” Microsoft said it was working with an organization that is addressing this issue.

The authors of the study aren’t satisfied with the responses. Mark Dummett, Business and Human Rights Researcher at Amnesty International points out the unsettling juxtaposition. “The glamorous shop displays and marketing of state of the art technologies are a stark contrast to the children carrying bags of rocks, and miners in narrow manmade tunnels risking permanent lung damage,” he says.

While he doesn’t accuse the companies of ignoring these facts outright, he does consider it their job to make sure the children are removed from the mines and the other working conditions for everyone else are improved. “Millions of people enjoy the benefits of new technologies but rarely ask how they are made,” he says. “It is high time the big brands took some responsibility for the mining of the raw materials that make their lucrative products.”

In a video about the working conditions, published on Monday, Dummett criticizes Sony, Samsung, Microsoft, and Volkswagen (who allegedly use the batteries for its smart cars) for implying (or, in Samsung’s case, outright stating) that it’s “impossible” to trace where the cobalt comes from.

Dummett responds, aptly: “If Amnesty International can do it, they can do it.”