What just happened? Amazon has been slammed for the "unethical and illegal" working conditions at one of its supplier factories in China. A nine-month investigation by the Observer and the New York-based China Labor Watch into the Hengyang Foxconn factory revealed a high number of low-paid, overworked agency staff making Amazon's speakers and e-readers.

The investigation discovered that 40 percent of the factory's workers were agency staff, who receive no sick pay and can be instantly let go when demand falls. China introduced a law four years ago that ensures these workers make up only 10 percent of a company's workforce---an attempt to stop firms from exploiting the temporary workers.

It was also found that overtime at the factory was being paid at a standard hourly rate, rather than the legally required time-and-a-half. In peak season, some employees put in 100 hours of overtime, and there were instances of people working 14 days in a row. Chinese law says monthly overtime cannot exceed 36 hours.

Workers at the factory also get lower wages than Foxconn employees in other Chinese locations. According to The Guardian, their standard 1750 yuan per month ($273) is less than the 2,400 yuan ($374) per month received by those at Foxconn's Shenzen factory, which manufactures Apple's products. That amount is around half the country's national living wage.

Other issues included employees not receiving adequate safety training, being required to arrive at their stations 10 minutes before their shifts begin and not being paid for this time, and a lack of fire safety precautions in staff dorms.

Amazon said it found two of the violations---excessive overtime and use of agency staff---during an audit of the factory in March. "We immediately requested a corrective action plan from Foxconn Hengyang detailing their plan to remediate the issues identified, and we are conducting regular assessments to monitor for implementation and compliance with our Supplier Code of Conduct," Amazon said. "We are committed to ensuring that these issues are resolved."

Foxconn said that it "works hard to comply with all relevant laws and regulations in all markets where we operate."