Senators are taking steps to investigate Facebook following reports that it knew Instagram, the company's photo-sharing app, has a negative effect on teens' mental health.

Researchers tapped by the tech giant to examine the app's impact on young users' mental health over the past three years found that 32% of teen girls who "felt bad about their bodies" said Instagram made the issue worse, according to company documents obtained by The Wall Street Journal.

Now, Sens. Richard Blumenthal, D-Conn., and Marsha Blackburn, R-Tenn., — chair and ranking member of a Senate commerce subcommittee on consumer protection — plan to investigate the tech giant over its knowledge of Instagram's impact on teens, and specifically, teenaged girls.

"Facebook knew this. They were watching. They were monitoring. But in search of that dollar and another dollar of profit, they did it anyway," Blackburn told Fox News of Facebook's internal Instagram report. "We've encouraged them not to market to children. We've encouraged them to restrict access and use for children [on] some of these platforms, but they've been hesitant to do that again because they're interested in profit."

Sen. Marsha Blackburn (R-TN) speaks during a Senate Judiciary Committee hearing on Capitol Hill in Washington, DC.

She added that because Facebook is aware of the issue, the Senate Commerce, Science and Transportation Subcommittee on Consumer Protection, Product Safety and Data Security is going to "ramp up … work on these issues of data security and privacy and online safety for children," looking specifically at "overexposure to screen time" and "the psychological impact" social media and gaming have on children.

She added that Instagram is not the only problematic app among young users. Snapchat, TikTok, Tumblr and even online games also pose risks to children's privacy and mental health, she said.

Blackburn, who has two children and three grandchildren, said she is "absolutely" concerned about how social media will impact her grandkids as they get older.

"I think we all do," she said. "Talk to any pediatrician. They will tell you: If you are not concerned, you need to start reading and become concerned. And I do believe that during the era of COVID with children doing school at home and parents being there to watch and see exactly what they were doing and the impact that that had — the way teachers handled this — I think that's had an impact on why people are paying so much more attention to the online privacy of children."

One 2019 slide on Instagram researchers' presentation to Facebook reviewed by the Journal said the app makes "body image issues worse for one in three teen girls."

Sen. Richard Blumenthal, D-Conn., speaks during a Senate Judiciary Committee hearing on Capitol Hill in Washington.

"Teens blame Instagram for increases in the rate of anxiety and depression," another slide read, according to WSJ. "This reaction was unprompted and consistent across all groups."

Some users also attributed time spent on the app to experiencing suicidal thoughts; 6% of American users indicated a connection between the two compared to 13% of U.K. users, the slide presentation reviewed by WSJ said.

Karina Newton, Instagram's head of public policy, said in a Tuesday blog post that it stands by its research on Instagram, which demonstrates the company's "commitment to understanding complex and difficult issues young people may struggle with, and informs all the work" Instagram does "to help those experiencing these issues."

About four in 10 Americans use Instagram compared to about seven in 10 Americans who use Facebook, according to a Pew Research survey published in April. Among young adult users between the ages of 18 and 29, the majority (81%) said they use Instagram.

More than 40% of the app's users are under 22 years old, and about 22 million teens use the app every day, WSJ reported, citing Facebook's documents. A 2018 Pew Research survey that Newton cited in her Tuesday blog post found that 81% of teens ages 13 to 17 found that social media in general makes them feel more connected while 26% said it makes them feel insecure.

Four in 10 teens said they only post on social media so that they look good to other people, and more than half of teens surveyed said they have "unfriended" or "unfollowed" other users due to bullying.

Apple iPhone XR showing Instagram application on mobile

"We’re proud that our app can give voice to those who have been marginalized, that it can help friends and families stay connected from all corners of the world, that it can prompt societal change; but we also know it can be a place where people have negative experiences, as the Journal called out today," Newton said in the blog post.

Blackburn, however, said Facebook has been working on issues surrounding mental health and data privacy for minors "forever" but have "not been able to police themselves or to take actions that are going to benefit the public writ large."