Wang, 43, co-founded Yantai Jinri OMY Construction Equipment Co. with Sun Weijie and Liu Zhenfeng in 1997.

FORBES: New Chinese Billionaire Emerges As Oil Services Company Yantai Jereh Soars

The company said the interns were employed at its factory in the city of Yantai in eastern China.

BBC: Foxconn

Foxconn said the interns were found by an in-house investigation at its factory in the eastern city of Yantai.

FORBES: China's Foxconn Weeds Out Underage Interns

Wu is looking to second-tier cities such as Yantai, Wuxi and Changzhou for growth as first-tier cities such as Beijing mature.

FORBES: Wu Yajun & family

For all its growth, Yantai Jereh is still a relatively small player.

FORBES: New Chinese Billionaire Emerges As Oil Services Company Yantai Jereh Soars

Scarabeo 9 is a semi-submersible drilling vessel recently built by Yantai Raffles, which will be on contract by Repsol YPF for deepwater exploratory drilling off Cuba.

FORBES: Cuba Chases 5 Billion Barrels of Undiscovered Oil; U.S. Groups Respond

Two years later, they founded Yantai Jereh, which grew into a major supplier of oilfield equipment and services for oil and gas drilling, natural gas liquefaction and environmental control.

FORBES: New Chinese Billionaire Emerges As Oil Services Company Yantai Jereh Soars

Wang Kunxiao, president of Yantai Jereh Oilfield Services Group (Jereh), has become a new billionaire as shares of the Chinese oil and gas service provider he co-founded with fellow billionaire Sun Weijie surged more than 60% this year amid an shale gas equipment boom in China.

FORBES: New Chinese Billionaire Emerges As Oil Services Company Yantai Jereh Soars