Amazon’s Prime Day is pretty fantastic for customers. It’s the time to shop for tech, fun summer yard furniture, or even that coveted big-screen TV you’ve been eyeing all year. But as it turns out, it’s not so fantastic for Amazon workers.

According to a new report, Prime Day is the cause of a massive number of injuries for warehouse workers.

On Tuesday, the Senate’s Health, Education, Labor, and Pensions (HELP) Committee released the interim results of a yearlong investigation into Amazon’s warehouse conditions for workers, which just so happened to overlap with Prime Day (July 16 and 17).

According to internal data provided by Amazon from Prime Day 2019, “just under” 45 total injuries per 100 workers were documented, or “nearly half of the company warehouse workers,” the report states. The total injury rate includes injuries that Amazon is not required to report to the Occupational Safety and Health Administration (OSHA), including nonserious injuries like paper cuts, scrapes, and bruises.

The rate of injuries that the company is required to report to OSHA was more than 10 injuries per 100 workers—”more than double the industry average.”

Senator Bernie Sanders, chair of the HELP committee, called out Amazon’s treatment of workers in a fiery statement. “Amazon continues to treat its workers as disposable and with complete contempt for their safety and well-being,” Sanders said. “That is unacceptable, and that has got to change.”

In a statement, Amazon spokesperson Kelly Nantel said the Senate’s report “ignores our progress and paints a one-sided, false narrative using only a fraction of the information we’ve provided,” and that “since 2019, we’ve made significant progress—reducing our recordable incident rate (which includes anything that requires more than basic first aid) in the U.S. by 28%, and our lost-time incident rate (which only includes more significant injuries that require an employee to miss at least one day of work) by 75%.”

According to the report, it’s not just a matter of a few too many accidents. It argues that understaffing, particularly during Amazon’s busiest times, is a clear culprit. The report alleges that having too few employees has led to worker endangerment, as employees “have to manage increased volume without increased support.” It even points to an internal Amazon document, titled, “2021 Prime Day Lessons Learned,” which shows Amazon “met only 71.2% of its hiring target” between May and June of 2021.

The report explicitly calls out the company for requiring employees to move at an unrealistic pace during the busiest times of the year, when demand multiplies. And it provides details from some of the hundreds of past and present Amazon employees who say the company put them in danger.

“These workers not only confirmed that the company sets unsustainable productivity requirements and that serious injuries are common, they also told Committee staff that Amazon’s busiest periods—Prime Day and the holiday season—are by far the most dangerous,” the report says.

One employee spoke about the company failing to install an automatic stop feature on a new conveyor belt, in an effort to get it up and running quicker. Not including the feature meant “the belt wouldn’t stop if there was a jam,” the employee said, citing just one example of the unsafe conditions to which they said employees were routinely subjected.

In addition to documenting understaffing and a preference for speed over safety, the report also alleges that Amazon underreported injuries to OSHA. The U.S. Department of Justice is investigating the issue.

While it’s certainly not the first time Amazon has come under fire for its treatment of workers, the report appears to demonstrate that the multibillion-dollar corporation is still not doing enough to protect its workers from harm, and putting profit and productivity over employee safety and well-being.