Children as young as seven years old are working for up to $2 daily mining in dangerous conditions to gather cobalt used in lithium batteries for 16 multinational corporations like Apple, Microsoft, Samsung, Sony, and others, according to Amnesty International.

If true, a report by the human rights group about mining conditions in the Democratic Republic of Congo counters claims by gadget producers that child labor is not involved in their production stream. The report said at least 80 miners have died in the past year in the DRC, which produces about half the world's cobalt. Unicef estimates that there are as many as 40,000 child miners in the region. Amnesty International interviewed dozens of workers, who usually wear no protective clothing while toiling long hours.

A 14-year-old orphan named Paul said he works so long underground that "I had to relieve myself down in the tunnels," according to the report. "I would spend 24 hours down in the tunnels. I arrived in the morning and would leave the following morning," the boy told Amnesty International.

A host of responses from implicated companies (all included in the report) suggests that they were unaware of child labor and harsh mining conditions because of, among other things, the complexities in the supply chain.

Apple told Amnesty International that it is "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." Vadophone told Amnesty International that it "is unaware as to whether or not cobalt in our products originates in Katanga in the DRC… both the smelters and the mines from which the metals such as cobalt are originally sourced are several steps away from Vodafone in the supply chain."

Samsung, Microsoft, and Sony all commented as well.

"In reality, it is very hard to trace the source of the mineral due to the suppliers' nondisclosure of information and the complexity of the supply chains. Therefore, it is impossible for us to determine whether the cobalt supplied to Samsung SDI comes from DRC Kataanga's mines," Samsung told Amnesty International.

Microsoft said, "We have not traced the cobalt used in Microsoft products through our supply chain to the smelter level due to the complexity and resources required."

Finally, Sony commented, "We are working with the suppliers to address issues related to human rights and labor conditions at the production sites, as well as in the procurement of minerals and other raw materials."

Mark Dummett, business and human rights researcher at Amnesty International, expressed dismay at the situation. "What is very worrying is that none of the companies that we identified through our research and named in investor documents could trace the cobalt they use in their products back to the mines where it originated," he wrote. "Around half of all cobalt comes from the DRC, and no company can validly claim that they are unaware of the human rights and child labor abuses linked with mineral extraction in the region."

The report said miners, both adults and children, usually worked 12-hour, back-breaking days under life-threatening conditions. Often, the work happened during intense heat without gloves and face masks.

There is an estimated $24 trillion worth of untapped minerals in the Democratic Republic of Congo. Here is a briefing about cobalt use in batteries.