Thirteen states and the District of Columbia sued TikTok on Tuesday, accusing the company of creating an intentionally addictive app that harmed children and teenagers while making false claims to the public about its commitment to safety.

In separate lawsuits, a bipartisan group of attorneys general cited internal company documents to paint a picture of a multibillion-dollar company that knowingly contributed to a mental health crisis among American teenagers to maximize its advertising revenue. They said that TikTok, which is owned by the Chinese company ByteDance, had relentlessly designed features to prompt heavy, compulsive use of TikTok and that many children were using the app late at night when they would otherwise have been asleep.

TikTok “knew the harms to children,” Rob Bonta, the Democratic attorney general of California, said in an interview. “They chose addiction and more use and more eyeballs and more mental and physical harm for our young people in order to get profits — it’s really that simple.”

The lawsuits add to a rapidly expanding list of challenges in the United States for TikTok, which now has 170 million monthly U.S. users. A federal law passed in April calls for the app to be banned in the United States as of January unless it is sold. A federal lawsuit against the company in August also claimed that TikTok allowed children to open accounts, gathered information about them and made it difficult for their parents to delete the accounts.

TikTok said that it strongly disagreed with the claims in the lawsuits and that it provided “robust” safeguards for young users.

“We’re proud of and remain deeply committed to the work we’ve done to protect teens, and we will continue to update and improve our product,” Alex Haurek, a spokesman for the company, said in a statement. He added that TikTok had tried to work with the attorneys general for more than two years and found the lawsuits “disappointing.”

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