In a new interview with Yahoo Finance, California Attorney General Rob Bonta explained why he and eight other attorneys general are investigating the effects of short-form video site TikTok on young users.

“There is mounting evidence, as we've seen — that of the devastating toll that social media has on our children's mental health and their well being,” Bonta told Yahoo Finance Live on Thursday. “And we want to know what TikTok knew about those harms to children, when they knew it, and what they did to increase engagement among our children.”

The bipartisan group of U.S. state attorneys general want answers from ByteDance’s popular video-sharing platform TikTok to evaluate suspected harm the social media platform is causing to children and whether it's violating U.S. consumer protection laws. TikTok attracts a large audience of minors to its platform. As of September, approximately 25% of its users were between 10 and 19 years old, according to Statista.

The investigation comes amid increasing scrutiny over the effects of social media on the mental health of young people, a danger President Joe Biden warned about just Tuesday in his State of the Union address. And last month, Senators proposed legislation aimed at shielding children from dangers associated with social media, a topic that's been the subject of multiple Congressional hearings.

In a statement to Yahoo Finance, ByteDance said, “We care about building an experience that helps to protect and support the well-being of our community and appreciate that the state attorneys general are focusing on the safety of younger users.” The company went on to say that it limits its features by age, provides tools and resources to parents, and designs policies with the well-being of young people in mind.

Bonta said while he appreciates that ByteDance intends to work with the attorneys general in their investigation, the company needs to show data to back up its words.