Discord is one of the biggest apps out there.

The FBI is reportedly investigating certain groups using the popular chat application Discord, according to Forbes.

The report alleges that a large number of individuals are using the application for cybercriminal activity, such as stealing usernames, passwords, and other personal information. Child predators are also lurking on the chat service, the report says, targeting Discord’s youngest users.

“Though we do not read people’s private messages, we do investigate and take immediate action against any reported violation by a server or user,” a Discord spokesperson told Forbes. “[This] can include shutting down offending servers or banning users.”

Discord is one of the biggest chat apps available today with millions of people using it. The app was valued at over $2 billion in December following another successful fundraising round.

Discord has also been looking to maximize its popularity over the past year by opening its own store and launching its activity window—among other features that the company hopes will help bring more potential users to the app in the future.