(Bloomberg) A watchdog group is calling on Amazon.com Inc. to improve conditions for factory workers in China who make Echo speakers and Kindle e-readers, renewing criticisms that CEO Jeff Bezos became the world’s wealthiest man on the backs of low-paid laborers.

The New York-based China Labor Watch released a report at the weekend following a nine-month investigation of working conditions at a factory in the city of Hengyang owned by Hon Hai Precision Industry Co., the company known as Foxconn, which manufactures products for Amazon. It offers the first behind-the-scenes glimpse of how Amazon produces voice-activated speakers that cost as little as $40.

The report paints a picture of low pay and intense working conditions.

Note: Read our discussion guidelines before commenting.