A group of attorneys general from 45 U.S. states and Washington, D.C., demanded Monday that social media app TikTok produce materials as part of an investigation into its effect on young users’ mental health.   

“We know that social media is taking a devastating toll on young people’s mental health and well-being, and through our investigation we are getting a clearer sense of TikTok’s role,” California Attorney General Rob Bonta said in a statement.   

The investigation began last year when eight states, including California, Massachusetts and Tennessee, launched a bipartisan probe of TikTok, focusing on whether the popular video-sharing app is endangering young people and violating state consumer protection laws.    

On Monday, Tennessee Attorney General Jonathan Skrmetti asked a Tennessee court to order TikTok to produce subpoenaed materials sought by the investigation. Attorneys general from across the United States filed a brief in support of the motion to compel TikTok to hand over the information.    

The Tennessee court petition alleges that TikTok has failed to preserve potentially relevant evidence in the investigation, including internal employee chat messages.   

It says TikTok has shared some internal messages in response to its request but said the company has rendered them “unrecognizable and nearly incomprehensible.”   

TikTok has not commented on the case.   

“We need to know more about the company’s business practices so we can keep our kids safe,” North Carolina Attorney General Josh Stein said in a statement Monday.   

California’s Department of Justice said in a statement that heavy use of social media is “strongly associated with self-harm, depression, and low self-esteem in teens — and every additional hour young people spend on social media is associated with an increased severity of the symptoms of depression.”   

The latest court challenge comes as TikTok, owned by Chinese tech company ByteDance, faces security concerns. The United States, Canada and the European Union have all banned the use of the app on government-issued devices.    

Like other social media apps, TikTok has also received criticism that it is not doing enough to protect younger users from inappropriate content.   

Last week, TikTok said it was developing a tool that would allow parents to block certain content on the app. The company also said parents will now be able to set time limits on the app for their teens, depending on the day of the week.   

Some information in this report came from Reuters.