Foxconn employees on the assembly line in Longhua, Shenzhen, China. The company reportedly employed students working overtime at its iPhone factory in Zhengzhou.
Qilai Shen | Bloomberg | Getty Images

Apple's major supplier Foxconn said on Thursday a "technical error" occurred when hiring new recruits at a major iPhone factory in China and offered an apology, one day after the company was rocked by fresh worker unrest.

Hundreds of workers joined protests at Foxconn's flagship iPhone plant in China's Zhengzhou, with some men smashing surveillance cameras and windows, footage uploaded on social media showed.