The Department of Justice is suing TikTok for allegedly letting kids under 13 make accounts without their parents’ permission and collecting “extensive data” on them, in violation of US child privacy law.

The DOJ claims that TikTok knowingly let kids onto its platform through its “Kids Mode,” collected their information, and failed to delete their accounts at their parents’ requests, in violation of the Children’s Online Privacy Protection Act (COPPA). When a kid under 13 entered their age on the app, they’d be prompted to enter a username, which doesn’t contain personal information, and it would create a Kids Mode account for the user. But the app wouldn’t notify parents or get their consent. Kids can’t upload videos in that mode, but they can view videos; the DOJ alleges that TikTok collected some personal information on them as part of this process, like unique device identifiers and IP addresses.

The lawsuit alleges that TikTok’s age-gating techniques “are deficient in multiple ways.” Under an earlier practice, TikTok would let users restart the account creation process even if they’d originally entered a birthday showing they’re under 13, according to the complaint. TikTok also used to let users log in through Instagram or Google, which would categorize the accounts as “age unknown,” the DOJ alleges.

The DOJ says TikTok has let millions of kids use its platform but said it’s hard to pin down the exact scale of its violations because it didn’t comply with a requirement from a 2019 injunction to keep records on its COPPA compliance. The DOJ is asking the court to prevent TikTok from violating COPPA in the future and pay civil penalties for each violation. Under the FTC Act, civil penalties can go up to $51,744 per violation, per day.

The Federal Trade Commission took credit for its investigation leading to the complaint. The agency announced in June that it had referred a complaint against TikTok to the DOJ after an investigation of potential violations under the FTC Act and COPPA. At the time, the FTC said it had “uncovered reason to believe” TikTok was “violating or are about to violate the law.”

TikTok spokesperson Alex Haurek said in a statement that the company disagrees with the DOJ’s claims, “many of which relate to past events and practices that are factually inaccurate or have been addressed. We are proud of our efforts to protect children, and we will continue to update and improve the platform. To that end, we offer age-appropriate experiences with stringent safeguards, proactively remove suspected underage users, and have voluntarily launched features such as default screentime limits, Family Pairing, and additional privacy protections for minors.”