Foxconn the Taiwan-based contract manufacturer announced on Sunday that it was investigating one of its plants in China where devices are made for Amazon.com, after a watchdog group in the US criticized what it called harsh labor conditions at the plant.
The China Labor Watch found workers earn about £233 a month, less than half the national living wage of £530, calculated for China by the Asia Floor Wage Alliance.
In violation of Chinese laws, workers put in 100 hours a month (36 hours is the legal limit) of overtime during peak periods, with some employees operating for 14 days straight.
It was also noted that the workers at Hengyang were being paid significantly less than workers at other Foxconn factories.
"All workers are subject to long hours and low wages", according to the report.
Foxconn says via an exchange filing it has begun its own internal investigation.
In its statement to the British publication, Amazon said: "Amazon takes reported violations of our supplier code of conduct extremely seriously". A lot of them were working 14 hour weeks without a single day off and had to ask for permission to visit the restroom.
Such staff were paid overtime at the normal rate, not the 1.5x rate required both by Chinese law and the Amazon code of conduct for suppliers.
The violations were said to be taking place at a Foxconn factory in Hengyang in Hunan province that is involved in production of Amazon devices. The concerns involved treatment of dispatch workers and overtime pay, Amazon spokesman Ty Rogers said.
While working conditions in Chinese factories have been a point of concern for quite some time, with companies like Apple, Nike, Foxconn and a host of other brands having been in the spotlight recently, Amazon has now been highlighted by New York-based China Labor Watch in a report released this weekend.
The watchdog group China Labor Watch, based out of NY, released a study over the weekend relating the conditions under which workers in the factory function. "We are committed to ensuring these issues are resolved".
In the years after, rights groups and workers said conditions at the plant had improved.
Kara Hartnett Hurst, Amazon's head of worldwide sustainability, wrote back saying: "Amazon recognizes our responsibility to ensure the well-being of factory workers manufacturing products for Amazon".
Foxconn, meanwhile, said that it "works hard to comply with all relevant laws and regulations" where it operates and conducts regular audits. It added that regular audits were carried out "and if infractions are identified, we work to immediately rectify them".