In November 2012, Samsung established a code of conduct for suppliers in line with standards set by the Electronic Industry Citizenship Coalition. It also asked suppliers to sign a compliance agreement to prevent child labor.

In addition, Samsung demands that suppliers adopt a strict hiring process that includes face-to-face interviews and the use of scanners to detect fake IDs to ensure no child laborers are hired.

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In its annual sustainability report, published on June 30, the firm said a third-party audit of 100 Chinese suppliers found no instances of child labor.

The report, however, cited other problems, such as with minors of legal working age found handling chemicals at 48 suppliers, as well as a majority of suppliers not complying with China's laws on overtime.

Samsung said it has demanded immediate action to correct such behavior.

But China Labor Watch Executive Director Li Qiang said last week that Samsung's social responsibility reports were an "advertisement" and that its efforts have so far failed to bring improvements for workers.

"What Samsung says is not important; what's important is their actions," Li said.

The watchdog's report said the child workers it found working at Dongguan Shinyang were being paid about two-thirds of what adult employees would be paid in weekly wages despite doing the same work. The child workers also were not served proper food at the factory cafeteria due to their night shift hours.

Samsung declined to comment on details of its investigation and whether confirmation of child labor would affect its existing relationship with parent Shinyang Engineering, which also is a Samsung supplier.

"Samsung will strengthen its hiring process not only at its production facilities but also at its suppliers to prevent such (cases) from reoccurring," the company said.