Washington State Department of Labor and Industries inspectors found that Amazon required workers execute repetitive motions, lifting and other physical work at a fast pace.
Experts say that puts workers at the risk of developing work-related musculoskeletal disorders (WMSDs).
Amazon's Spokane fulfillment center employs about 2,400 workers. In the last three years of operation, there have been 400 worker's compensation claims for the type of injury known as WMSD.
Labor and Industries has previously cited other Amazons in Washington. All have revealed that the company was aware of these hazards.
State officials say they consider this most recent violation is to be willful and, for that reason, assessed a higher penalty.
Apart from the fine related to putting workers at risk, they were also fined for noise levels that were too high for workers not wearing appropriate hearing protection.