The Senate Judiciary Committee will hold a hearing on online child sexual exploitation on December 6 and the CEOs of major tech companies are set to testify. The committee expects Meta CEO Mark Zuckerberg and his counterpart at TikTok, Shou Zi Chew, to testify voluntarily. It also wants to hear from the CEOs of X (formerly Twitter), Discord and Snap, and it has issued subpoenas to them.

“Big Tech’s failure to police itself at the expense of our kids cannot go unanswered,” committee chair Sen. Dick Durbin (D-IL) and ranking member Sen. Lindsey Graham (R-SC) said in a joint statement, as Reuters reports. “I’m hauling in Big Tech CEOs before the Senate Judiciary Committee to testify on their failure to protect kids online,” Durbin wrote on X.

According to the committee, X and Discord refused to accept service of the subpoenas on their CEO’s behalf, “requiring the committee to enlist the assistance of the US Marshals Service” to serve them personally. “We have been working in good faith to participate in the Judiciary committee’s hearing on child protection online as safety is our top priority at X,” Wifredo Fernandez, head of US and Canada government affairs at X, told Engadget in a statement. “Today we are communicating our updated availability to participate in a hearing on this important issue.”

“Keeping our users safe, especially young people, is central to everything we do at Discord,” a Discord spokesperson told Engadget. “We have been actively engaging with the Committee on how we can best contribute to this important industry discussion. We welcome the opportunity to work together as an industry and with the Committee.”

The issue of tech platforms allegedly facilitating harms against kids has become an increasingly pressing issue. Earlier this month, former Meta executive Arturo Béjar testified that Zuckerberg failed to respond to his email detailing concerns about harms facing children on the company’s platforms. Senators then demanded documents from the company’s CEO “related to senior executives’ knowledge of the mental and physical health harms associated with its platforms, including Facebook and Instagram.”

Update 11/20 3:40PM ET: Added Discord’s statement.