Human rights organization Amnesty International has alleged that high-profile companies including Apple, Samsung, Sony and Microsoft have failed to check to make sure that child labor is not involved in mining the minerals used in the production of their devices.

A report by Amnesty found that cobalt mining operations in the Democratic Republic of Congo employ children as young as 7 years old to work in high-risk conditions. UNICEF believes that about 40,000 children are employed as miners across southern DRC.

Miners are exposed to conditions that could bring long-term health in addition to the constant threat of a fatal accident. Amnesty claims that at least 80 miners have died underground from September 2014 to December 2015 in the southern part of the country.

Congo produces at least half of the world's supply of cobalt, which is an important component in the manufacturing of lithium-ion batteries for devices such as smartphones and tablets.

"It is a major paradox of the digital era that some of the world's richest, most innovative companies are able to market incredibly sophisticated devices without being required to show where they source raw materials for their components," said Africa Resources Watch's Executive Director Emmanuel Umpula.

The companies responded by saying that they are fully against the practice of child labor, with Apple issuing a statement that underage labor is not tolerated in the company's supply chain.

Apple added that the company carries out stringent audits across its supply chain, with suppliers that are found to be practicing child labor being required to fund the return home of the underage employee, finance the child's education at an institution chosen by the child or his/her family, continue with the payment of the child's wages and offer the child a job once he or she reaches the legal age to be part of the workforce.

Samsung likewise said that it has a "zero tolerance policy" for child labor, adding that, like Apple, it has audits in place across its supply chain. The company said suppliers that were found to be using child labor will have all contracts with Samsung terminated immediately.

Sony, on the other hand, said it is working with suppliers to address the child labor issues related to mineral procurement.

Microsoft, meanwhile, admitted that it is extremely challenging to track the origin of the cobalt used down to the exact area where the material was mined because of the complexity of the company's supply chain and the co-mingling of the materials within regions.

The 16 multinational companies included in the Amnesty report, aside from the aforementioned, include Ahong, BYD, Daimler, Dell, HP, Huawei, Inventec, Lenovo, LG, Vodafone, Volkswagen and ZTE.