Hong Kong (CNN) -- Foxconn Technology Group -- the world's largest electronics manufacturer and supplier to companies like Apple, Samsung and Microsoft -- admitted that interns as young as 14 worked at one of its Chinese plants.
"An internal investigation carried out by our company has confirmed media reports in China that some participants in the short-term student internship program that is administered at our campus in Yantai, Shandong Province are under the legal working age of 16 years," the company said in a statement. "This is not only a violation of China's labor law, it is also a violation of Foxconn policy and immediate steps have been taken to return the interns in question to their educational institutions."
The underage interns had worked at the plant for about three weeks, the company said. No evidence was found at other plants in China, the company added.
Foxconn is one of the world's largest suppliers of components for the electronics industry. Much of its manufacturing division is based in mainland China, where it assembles a range of products including Apple's iPhone and iPad, Amazon's Kindle and Microsoft's Xbox.
Interns represent about 2.7% of Foxconn's 1.2 million employees in China.
The report was the latest in a string of incidents for Foxconn. Earlier this month, workers rights groups and Chinese state media reported work stoppage at a Zhengzhou plant regarding "overly strict demands" for production of Apple's iPhone. The company disputed reports of a "strike," but admitted employee "disputes." Last month, a factory in Taiyuan was shut down for a day after a large-scale brawl sent 40 people to the hospital.
Working conditions at Foxconn factories have been under the spotlight since a 2010 spate of worker suicides at its plants. Foxconn said it had increased workers pay, introduced counselors, started a 24-hour phone counseling service and opened a stress room where workers can take out frustration on mannequins with bats.
The Fair Labor Association -- an industry-funded labor watchdog whose membership includes Apple, a large customer of Foxconn -- released a report in August that Foxconn has moved to bring working hours including overtime down to below 60 hours per week "with the goal of reaching full compliance with the Chinese legal limit of 40 hours per week, plus an average of 9 hours of overtime per week while protecting worker compensation."
"Immediate health and safety measures" had been made, such as enforcement of breaks, changing equipment design to reduce repetitive stress injuries and testing of emergency equipment like eyewashes and sprinklers, the August report said.
An explosion last year at a Foxconn plant that makes Apple's iPad2 in Chengdu killed four people and injured 18 more. Chinese officials said the blast may have been caused by combustible dust in a polishing workshop. That incident followed a report by a labor group alleging that workers at the same plant do not have adequate training in the use of chemicals and do not have regular on the job health checks.