A sweeping congressional investigation into worker safety at Amazon found that the nation’s largest online retailer manipulated data on warehouse worker injuries and disregarded internal research on improving safety.

The report was released late Sunday by the Senate Health, Education, Labor and Pensions (HELP) Committee, chaired by Sen. Bernie Sanders (I-Vermont).

“In its endless pursuit of profits, Amazon sacrifices workers’ bodies under the constant pressure of a surveillance system that enforces impossible rates,” Sanders said in a written statement.

The committee found that Amazon workplaces recorded 30 percent more injuries in 2023 than the warehousing industry average and that the company cherry-picks statistics to hide the fact that its warehouses are significantly more dangerous than other companies’ facilities.

A Washington Post analysis of federal data in 2021 found that Amazon’s injury rates were nearly double those of other businesses in the warehousing industry.

Amazon has previously disputed that analysis, saying in 2021 that it was “continuously learning and seeing improvements through ergonomics programs, guided exercises at employees’ workstations, mechanical assistance equipment, workstation setup and design, and forklift telematics and guardrails.”

The committee’s report is based on an investigation launched in June 2023 that looked back over seven years of Amazon workplace injury data.

Senate staffers interviewed more than 130 Amazon workers. Some reported that work injuries resulted in chronic pain and long-term disabilities, or made them unable to leave home or complete basic tasks.

The investigation also drew on about 280 documents provided by the company, though staffers said Amazon declined to provide much of the requested information. The committee used its subpoena power this year to request documents from a private hospital network facing allegations of understaffing, but it didn’t in the Amazon case because of political headwinds, staffers said.

Amazon said it cooperated with the investigation and provided thousands of pages of documents, but disputed the committee’s findings.

“Sen. Sanders’ report is wrong on the facts and weaves together out-of-date documents and unverifiable anecdotes to create a preconceived narrative that he and his allies have been pushing for the past 18 months,” company spokesperson Kelly Nantel said in an emailed statement Sunday.

She said that there is “zero truth to the claim that we systemically underreport injuries” and that Amazon’s expectations for employees “are safe and reasonable.”

As evidence, Nantel cited a recent decision by a Washington state judge to dismiss a state health and safety regulator’s allegations of serious ergonomic safety violations against Amazon.

The company also noted that it employs 800,000 front-line employees in the United States — and that the roughly 130 workers interviewed for the investigation represent about 0.018 percent of its hourly workforce.

Amazon founder Jeff Bezos owns The Washington Post.

The committee’s report found that on multiple occasions, Amazon neglected to implement worker safety measures recommended by its own research.

An internal study in 2021, known as Project Elderwand, estimated that workers who locate and pull items off shelves could make 1,940 repetitive movements in a 10-hour shift before their risk of lower-back injury increased, according to the report.

But the report said documents show that Amazon never enacted rules to prevent workers from exceeding that limit because of the potential impact on “customer experience.” The committee also said workers, in interviews, reported regularly exceeding the limit.

A second internal study, launched in 2020 and known as Project Soteria, identified risks for warehouse worker injuries and proposed changes to decrease injury rates, including a slower pace of work. Amazon rejected that, the committee found.

The investigation also found that Amazon discouraged and delayed injured workers from accessing outside medical care and repeatedly declined disabled workers’ requests for appropriate workplace accommodations.

“I don’t even use Amazon anymore, I’d rather wait … than have some poor employee in an Amazon warehouse get battered and bruised so I can get my book within six hours,” one worker told the Senate committee. “People don’t see that, they think it just appears by magic. But it doesn’t, it appears by blood, sweat, and tears.”

Nantel, the Amazon spokesperson, said Project Soteria wasn’t adopted because an internal team that evaluated its work and findings “determined they weren’t valid.” Elderwand, meanwhile, was a pilot program to test the impact of “microbreaks” on musculoskeletal disorders that “showed that the intervention was ineffective,” Nantel said.

Amazon has been under intense scrutiny for its safety record in recent years. In addition to the new Senate committee report, the U.S. attorney for the Southern District of New York has been investigating allegations that the company intentionally underreports worker injuries. A spokesperson for the Justice Department did not respond to a request for comment.

In June, Amazon was fined $5.9 million by California for failing to comply with a new state law aimed at protecting workers from productivity quotas that pose a risk to worker health and safety.

It is unclear whether the incoming Trump administration, empowered by a newly Republican-controlled Congress, will place the same scrutiny on Amazon’s labor practices as the company experienced under President Joe Biden.

Sen. Bill Cassidy (R-Louisiana), who is seen as an ally of business, is poised to replace Sanders as chair of the HELP Committee when President-elect Donald Trump takes office next month.

Trump has forged unusual ties for a Republican with some labor unions, including the Teamsters, which is highly critical of Amazon. But he is considering Heather MacDougall, a former Amazon vice president overseeing workplace health and safety, to lead the Occupational Safety and Health Administration, The Post reported last week.