Twitter does not delete an overwhelming majority of antisemitic tweets published on its platform, a study by the Anti-Defamation League (ADL) found on Thursday.

Over a nine week span, the ADL’s Center for Technology and Society (CTS) identified and reported 225 antisemitic tweets that accused Jews of everything from pedophilia and controlling the world to exaggerating the horrors of the Holocaust. Only 11, or just 5%, were removed, the group said.

“Twitter has taken some positive steps in the recent past. However, this report shows it has significantly more to do,” the ADL said. “Twitter must enact its most severe consequences and remove destructive, hateful content when reported by experts from the communities most impacted by such content.”

The group collected 1% of all Twitter content posted during twice-weekly, 24-hour periods over the nine week window. Those posts were fed through the group’s Online Hate Index, which it describes as a machine learning “antisemitism classifier.” Flagged tweets were then reviewed by human experts before being reported to Twitter.