(Reuters) -A bipartisan group of U.S. senators demanded Meta Platforms hand over internal assessments of how its products affect children and the effectiveness of its parental controls, according to a letter seen by Reuters.

The 10 senators led by Marsha Blackburn, a Republican from Tennessee, made the demand a week after a Senate hearing where former Meta safety researchers said the company shut down internal research showing Meta knew children were using its VR products and being exposed to sexually explicit material.

"Parental controls, instead of being the solution for Meta's rampant dangers-as they had been branded to both parents and to Congress-appear to be ineffective and underutilized," the senators wrote.

The demand adds to mounting pressure on Meta after Reuters reported last month that an internal policy document permitted the company's chatbots to "engage a child in conversations that are romantic or sensual." 

Meta has said the examples reported by Reuters were erroneous and have been removed, and that there was never a blanket prohibition on conducting research with young people. 

Senator Chuck Grassley, a Republican from Iowa who leads the Senate Judiciary Committee, and Senator Richard Durbin from Illinois, the committee's ranking Democrat, were among those who signed the letter on Tuesday demanding Meta disclose internal research applications and whether those requests were denied or modified.

The probe is part of broader scrutiny into AI chatbots' effects on children - including a separate Senate hearing on Tuesday where parents who sued OpenAI and Character.AI to hold them liable for their children's deaths by suicide.

Both companies have expressed their condolences and said they are improving their safety standards.