Three United States senators wrote a letter to Amazon CEO Jeff Bezos calling for the online marketplace to remove illegal and unsafe products and to provide accurate warnings to shoppers.

The letter comes after a recently published Wall Street Journal investigation found more than 4,000 items for sale on Amazon that were deemed unsafe by regulators or deceptively labeled.

The senators include a list of questions for Bezos to answer by September 29, such as why Amazon's safety measures have failed to prevent such products from being sold.

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Three United States senators wrote a letter to Amazon CEO Jeff Bezos on Thursday calling for the company to remove illegal and unsafe products from its store and to provide accurate warnings to shoppers. CNBC was the first to report on the letter.

"We write to you with grave concerns regarding Amazon's failure to remove from its platform illegal, deadly, and deceptive products, and to provide required visible warnings on products sold on your platform," read the letter, which was signed by three democratic senators: Connecticut Sen. Richard Blumenthal, New Jersey Sen. Bob Menendez, and Massachusetts Sen. Ed Markey.

The letter was written in response to an investigation from The Wall Street Journal published last week, which found thousands of items for sale on Amazon's platform that had "been declared unsafe by federal agencies." The investigation highlighted Amazon's lack of control over third-party vendors that sell products through its digital storefront, finding 4,152 items that federal regulators have found to be unsafe or that are "deceptively labeled."

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The Journal found that 116 products sold on Amazon's store between May and early August were incorrectly listed as being approved by the US Food and Drug Administration, including 98 eyelash growth serums and toys, which the agency doesn't even test. The newspaper also found 80 listings that matched the description of infant sleeping wedges that the FDA said could cause suffocation.

A 23-year-old man named Albert Stokes died in a motorcycle accident after a helmet he purchased on Amazon flew off during a crash, according to the Journal. The helmet was falsely labeled on Amazon as being compliant with the US Transportation Department, the report said.

"Unquestionably, Amazon is falling short of its commitment to keeping safe those consumers who use its massive platform," the senators wrote in the letter, which also notes that it's illegal to sell recalled items under the Consumer Product Safety Improvement Act of 2008.

"We invest significant resources to protect our customers and have built robust programs designed to ensure products offered for sale in our store are safe and compliant," Amazon said in a recent blog post about its product safety and compliance efforts.

The letter included a list of questions the senators demand that Bezos answer by September 29, such as why Amazon's current safety measures have failed to prevent unsafe, mislabeled, and recalled products from being sold. It also asks how Bezos will ensure that Amazon will not sell products deemed unsafe by the National Highway Transportation Safety Administration, the FDA, the Consumer Protection Safety Commission, and other federal agencies.

It's not the first time US senators have written to Bezos expressing concern over Amazon's practices. Earlier this month, Blumenthal and Menendez published a letter demanding answers about how the company decides which products are worthy of its "Amazon's Choice" badge.