Biel Crystal Manufactory -- which counts Apple, Samsung, HTC, and others as clients -- violates workers' rights, a Hong Kong rights group claims.
A report from a Hong-Kong watchdog group accuses suppliers of "military-style management of workers," despite Apple's code of conduct.
The contract manufacturer, which makes iPhones and other consumer electronics, acknowledges a "workplace issue" at a factory run by a supplier that reportedly makes iPhone connectors and other goods.
Despite Foxconn's efforts to improve working conditions at its factories, a watchdog group says it has found numerous faults.
In January, Apple's suppliers were 99 percent compliant with the requirement that no employee work more than 60 hours a week.
The lack of safety precautions for workers was most alarming at the company's Chengdu plant, according to a report released just two weeks before an explosion at the factory killed two.
One of the organization's employees also says Foxconn banned 16- and 17-year-old workers from overtime while inspections are ongoing.
Debby Chan, a human rights activist based in Hong Kong, has led the battle to improve conditions for employees of China's giant contract manufacturers
The factory that produces the iPhone and iPad has been accused of hiding child workers from labour inspectors.
Hardware giant still forcing its factory workers to toil under difficult conditions, according to a new report.