Labor group China Labor Watch released a report saying the Zhengzhou Foxconn factory in China — which it says is the largest Apple iPhone factory in the world — broke Chinese law by hiring too many temporary workers. The factory is operated by supplier Foxconn Technology Group.

Chinese law stipulates that dispatch workers (workers from staffing firms) shall not exceed 10% of total employed workers, but the percentage of dispatch workers at Zhengzhou Foxconn was around 50% in August, according to the report. It had been at 55% in 2018.

“Prior to 2016, Foxconn rarely recruited dispatch workers,” according to the report. “However, the percentage of dispatch workers at the factory now makes up 50% or more of the workforce.”

While hiring of temporary workers helps meet demand for building Apple products, it hurts wages overall at the factory, according to the report.

“The wages of dispatch workers are higher than regular workers, but dispatch workers are short-term workers and the factory does not need to increase the wages for all regular workers in the long-term,” it said. “Hence, the cost of employing dispatch workers is lower than recruiting more regular workers.”

Bloomberg reported that Apple said that after an investigation it found the percentage of dispatch workers exceeded its standards and is working with Foxconn to resolve the issue. However, Apple said that most of the other claims in the China Labor Watch report are false.