Amazon completed an audit of the factory in March and found violations regarding overtime and the use of dispatch workers, which it has asked Foxconn to remedy, it said in an emailed statement.

"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."

Salary reviews are conducted regularly and all full-time and temporary employees receive "both pre-job training and additional training in their assigned departments," Foxconn said in a June 10 statement.

The major electronics manufacturer in China, was criticised for poor working conditions in factories where Apple devices were made, leading to the company installing safety netting to prevent worker suicides. The findings at the Amazon device factory were similar, but less severe.

Echo speakers

Amazon, the world's biggest online retailer, sells a variety of devices. Kindles and tablets help it sell more digital books. It has sold tens of millions of Echo voice-activated speakers, which can be used to dim lights, stream music and order pizza.

Amazon also has faced criticism for working conditions in its US warehouses. One lawsuit alleged Amazon cheated workers out of pay by making them clock off before standing in security lines for theft-prevention measures before leaving the building. Amazon prevailed in that case before the Supreme Court, which ruled the workers were not entitled to payment for security screenings.

Bloomberg