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Amazon doesn't ask some toy sellers for proof of safety documents until after their toys have gone on sale on its site, according to a Wednesday report from CNBC. Some sellers had been asked to produce required safety documents only recently, for toys that'd already been available to buy on the platform for about two weeks, CNBC said.

The news follows a Wall Street Journal report last month that found Amazon had listed more than 4,000 banned and unsafe items for sale, including toys and medications that lacked warnings about their risks -- and some were even promoted as "Amazon's choice."

The sellers who spoke to CNBC said they received an email this month after already putting their products on sale.

"We are contacting you because we show that you may be selling items in the Toys category," the email reportedly says. "As part of our ongoing efforts to provide the best possible customer experience, we are confirming that your product meets the current mandatory safety standard."

Amazon told CNBC that it requires safety docs "very shortly" following a third-party product listing going live. The spokesperson reportedly said the emails weren't a reaction to the Journal's article.

"All products offered in our stores must comply with applicable laws and regulations, and we regularly contact selling partners to request safety documentation," Amazon said in an emailed statement.

An Amazon blog post last month in response to the Journal article said the e-tailer and tech powerhouse spent $400 million during 2018 on product safety and that it blocked more than 3 billion products before they were listed online.

"We require toys to be tested to relevant safety standards set by the Consumer Product Safety Commission," the blog post said. "Every few minutes, our tools review the hundreds of millions of products, scan the more than 5 billion daily changes to product detail pages, and analyze the tens of millions of customer reviews that are submitted weekly for signs of a concern and investigate accordingly."

Originally published Sept. 11, 11:56 a.m. PT.

Update, 12:07 p.m.: Adds statement from Amazon and info from blog post; 4:35 p.m.: Adds more detail