• Amazon was cited by the Labor Department at warehouses in New York, Colorado and Idaho.
• Federal safety inspectors found workers were exposed to unsafe conditions and ergonomic hazards.
• The probe follows an ongoing investigation by federal prosecutors into Amazon's warehouse safety.

Federal safety inspectors on Wednesday issued citations against Amazon at three of its warehouses for putting workers at risk of serious injury, the second such penalty in a month.

The Department of Labor's Occupational Safety and Health Administration said the e-retailer exposed workers at warehouses in Aurora, Colorado; Nampa, Idaho; and Castleton, New York to unsafe conditions and ergonomic hazards. The agency made the determination after reviewing on-site injury logs.

The move comes after OSHA last month cited Amazon for failing to keep workers safe at three other facilities.

Amazon faces up to $46,875 in proposed penalties for the violations announced Wednesday.

"Amazon's operating methods are creating hazardous work conditions and processes, leading to serious worker injuries," said Doug Parker, assistant secretary for Occupational Safety and Health, in a statement. "They need to take these injuries seriously and implement a company-wide strategy to protect their employees from these well-known and preventable hazards."

Amazon spokesperson Kelly Nantel said the company disagrees with OSHA's findings, saying they don't "reflect the reality of safety at our sites."

The company said it has taken steps to mitigate injuries in its facilities through things like job rotations, stretching, and engineering improvements that reduce the need to twist, bend or reach. Amazon also pointed to robotics systems that it has deployed in some warehouses, which it claims can improve safety in some repetitive tasks.

Amazon workers were at high risk of lower back injuries and other musculoskeletal disorders due to the frequency with which they lifted packages, handled heavy items, worked long hours and "awkwardly" twisted, bended and extended themselves to lift items, the agency said.

OSHA inspected the facilities after it received referrals from the U.S. Attorney's Office for the Southern District of New York. OSHA and the U.S. Attorney's Office in July opened an investigation into the three facilities. CNBC reported in August that the probe expanded to include three other sites, near Albany, New York, Denver, Colorado, and Boise, Idaho.

Amazon also faces a separate investigation by the U.S. Attorney's Office's civil division that centers around worker safety hazards at the e-retailer's facilities nationwide. As part of the probe, investigators are also looking into whether Amazon has accurately reported worker injuries and if it misrepresented those injuries to lenders to obtain credit.

OSHA cited Amazon in December for 14 recordkeeping violations and levied a proposed penalty of $29,008.

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