The alleged child-porn-trading users set up anonymous accounts with throwaway usernames or handles such as @dropbox_nudes_4_real (which has since been removed). The accounts that @ZZtails and other memers surfaced, which can also be found on the hashtag, contain blank posts with captions asking users to DM them for Dropbox links, which allegedly contain child porn or nudes.

“I’ll trade, have all nude girl videos,” one user commented in September 2018. “DM young girl dropbox,” said another. “DM me slaves,” said someone else. Many others commented “HMU to trade dropbox links” on various throwaway accounts. “Young boys only,” another user posted several times. On Saturday, an account with the username @trade_dropbox_linkz posted “DM if u want young girl links.”

According to screenshots shared with The Atlantic, several memers who reported the accounts received messages from Instagram claiming that the platform’s terms had not been violated. While they waited for Instagram to take action, meme-account holders banded together to spam related hashtags with memes. One memer who posted using the hashtag received a message from another user with links to illicit material, asking if he wanted to “trade boys.”

Late Monday night, after an inquiry from The Atlantic, Instagram restricted the hashtags #dropboxlinks and #tradedropbox. “Keeping children and young people safe on Instagram is hugely important to us,” an Instagram spokesperson said. “We do not allow content that endangers children, and we have blocked the hashtags in question.” The platform also said it is “developing technology which proactively finds child nudity and child exploitative content when it’s uploaded so we can act quickly.”

When reached for comment on Tuesday, a Dropbox spokesperson said, “Child exploitation is a horrific crime and we condemn in the strongest possible terms anyone who abuses our platform to share it. We work with Instagram and other sites to ensure this type of content is taken down as soon as possible.”

Read: Instagram has a massive harassment problem

“It’s just disgusting,” says Jacob, a 16-year-old who runs the meme account @Cucksilver. After searching the hashtag #dropboxlinks himself, Jacob said he was shocked at what it revealed. He posted several memes about it to his page, and reported the offending accounts.

Jackson Weimer, a college student and the founder of several meme pages, says he wasn’t surprised that meme accounts discovered the alleged problem before moderators from the platform itself. Memers usually follow a broad range of accounts and are intimately familiar with the platform’s dark corners. “Meme accounts do a good job of … bringing awareness to stuff that’s happening in the community. They do a good job of raising issues,” he says.

Part of the reason this particular issue spread so fast and so far is because many meme-account admins are teenagers themselves. “They could be the people at risk for this type of stuff,” Weimer said. “The fact that they’re so young makes them connect with those kids who are in danger and being taken advantage of via those hashtags.”