Amazon has removed dozens of listings for peptides, drugs that can be used for doping, after an investigation from The Markup found 66 examples of such products on the site. Peptides are made naturally in the body, but synthetic versions, which can be sold in vials and then reconstituted and injected, are often used as performance-enhancing drugs since they can speed recovery from injuries.

According to The Markup, in recent weeks Amazon had been carrying listings for peptides not on the US Food and Drug Administration’s list of approved drugs, months after telling the publication in May that it would start cracking down, and several of those drugs have been classified by the World Anti-Doping Agency as doping drugs. The drugs were labeled for “research” or “lab” uses, but questions on the products’ pages suggested people were ingesting the drugs.

“The products in question were previously allowed in our store for laboratory or research use only and not for human injection or consumption,” an Amazon spokesperson said in an email to The Verge. “However, out of an abundance of caution, we decided to no longer allow these products and have been removing them since, as we have in this case.”

The spokesperson added that third-party sellers on its platform are “independent businesses and are required to follow all applicable laws, regulations, and Amazon policies, including accurate detail page information, when selling in our store. We do not sanction customer misuse or abuse of products.”

A Wall Street Journal report last year found that Amazon was listing products via its third-party sellers that had been banned, mislabeled, or otherwise declared unsafe by US government agencies, including some imported prescription drugs.

Update September 17th, 7:34PM ET: Added comment from Amazon spokesperson