Alphabet Inc’s Google, Facebook Inc and Twitter Inc will testify next week before a U.S. Senate panel on efforts by social media firms to remove violent content from online platforms, the panel said in a statement on Wednesday.

The Sept. 18 hearing of the Senate Commerce Committee follows growing concern in Congress about the use of social media by people committing mass shootings and other violent acts. Last week, the owner of 8chan, an online message board linked to several recent mass shootings, gave a deposition on Capitol Hill.

The hearing “will examine the proliferation of extremism online and explore the effectiveness of industry efforts to remove violent content from online platforms. Witnesses will discuss how technology companies are working with law enforcement when violent or threatening content is identified and the processes for removal of such content,” the committee said.

Read more: Reuters