Within two hours of Twitter’s announcement that it had accepted Elon Musk’s $44 billion offer to buy the company and take it private, the first concerning signs flashed across Joe Mulhall’s screen. Mulhall is director of research at Hope Not Hate, a British antiracism and antifascism group that campaigns against bigotry.

When Musk heralded his purchase of Twitter by saying “free speech is the bedrock of a functioning democracy, and Twitter is the digital town square where matters vital to the future of humanity are debated,” Mulhall saw new accounts being set up on Twitter by previously banned far-right individuals and groups, including English far-right anti-Islam political activist Tommy Robinson and Britain First, a fascist political party. In the United States, other neo-Nazis that had previously been banned from the platform set up new accounts on Twitter.

The accounts were reported to Twitter by Mulhall, Hope Not Hate, and others and were subsequently banned before they could gain a foothold. But some worry this could signal a resurgence of people previously barred from Twitter for spreading hate and conflict, should Musk follow through with his promise to loosen rules around what kind of posts are permitted.

The ripple effects have already begun. On Monday, Christopher Bouzy, the founder of Bot Sentinel, a service that tracks inauthentic behavior on Twitter, noticed that a number of left-leaning accounts had already complained about losing followers. Bouzy noticed that he had lost 400 of his 77,000-odd followers. At first, he didn’t think it was a big deal: People churn through who they follow on a regular basis.

Bot Sentinel updates at midnight eastern time. When Bouzy looked at the data at 7 am, it became clear something more significant was happening. On a normal day, an average of around 750 accounts out of the roughly 2.5 million he samples are either deactivated or suspended.

The results by the end of April 25 were significantly different—5,132 accounts from across the political spectrum had been deactivated and a further 341 suspended. Other indicators looked strange as well. “We’re seeing this significant increase in right-wing accounts starting to follow these other accounts,” Bouzy says. “It could be a bat signal where they feel safe to come back to Twitter, or it could be something else going on.”

Manoel Ribeiro, who studies platform migration among the alt-right at the Swiss Federal Institute of Technology, Lausanne, terms it “replatforming.” “If Twitter adopts a free speech absolutist philosophy, it may very well be that decisions related to hate speech or incitement to harm will be reversed, reinstating popular far-right accounts,” he says.

The issue isn’t limited to the United States. Brazilian president Jair Bolsonaro has seen tenfold gains in his number of followers in the last two days, compared to his prior average, while Canadian premier Justin Trudeau lost followers on April 26, countering average daily gains. “It doesn’t make sense,” Bouzy says. “I don’t understand why Musk acquiring Twitter would have that effect on Brazilian politics.” Twitter confirmed to NBC News that the increase in account activity wasn’t automated and was organic churn that could be linked to Musk’s takeover of the platform.