China Labor Watch said in August that it had found seven workers under the age of 16 at a Samsung supplier based in the city of Huizhou. While Samsung said Monday its own investigation found no underage workers, it did discover instances of unsafe work practices and pledged to drop suppliers who fail to act when violations are uncovered.

in China has been on the rise amid reports of poor working conditions at factories. Apple has also come under fire, for conditions at factories run by its manufacturing partner Foxconn.

Samsung has 12 factories in China that it directly owns and operates, according to China Labor Watch. But the company also uses dozens of suppliers to manufacture products such as smartphones, displays, speakers and DVD players.

Workers at the factories are often stripped of their legal rights without their knowledge, according to the watchdog group. In many cases, workers sign incomplete contracts or have no contract at all with the factory or labor firm that placed them there.

China Labor Watch also accused Samsung of deliberately hiring only young female workers at its factories. It does this because they are "more cooperative and less able to defend their own rights," the labor group said. The recruiting ages can sometimes be between 16 and 23. Some factories were found hiring directly from vocational schools in China, a common practice among manufacturers there.