Members of Congress are pushing some of the country’s most powerful tech companies—Facebook, Google, Twitter, and Microsoft—to reveal how much they spend to keep terrorists from co-opting their platforms.

For years, and especially since the rise of ISIS, social media companies have taken heat for the way terror groups use them to find recruits and inspire attacks. The companies faced renewed scrutiny after a white supremacist terrorist killed 50 Muslims in two mosques. The killer live-streamed his rampage on Facebook, and the video stayed up there for about an hour; Facebook didn’t pull it down until New Zealand law enforcement reached out, and a Facebook rep said their algorithms couldn’t tell the video violated their terms of service because it wasn’t “particularly gruesome,” as The Daily Beast reported.

On March 27, representatives from the four companies –– who formed a counter-terror industry group called the Global Internet Forum to Counter Terrorism (GIFCT)––had a closed-door meeting with members of the House Committee on Homeland Security. Members asked the company’s representatives how much money they spend on efforts to block terrorists from using their sites, according to a person briefed on the conversation, and the representatives said they didn’t have that information available.

So on April 10, four Democratic committee members asked the companies to share details on how much they spend on counterterrorism.

“During a briefing to the Committee on March 27, 2019, your representatives conveyed your companies’ commitment to combating foreign and domestic terrorist content and other violent or hateful material on your platforms,” says the letter, which is addressed to the companies’ CEOs. “While we appreciated their strong words, we expect to see these verbal commitments backed up with financial resources, personnel, and technological investments.”

“As you all know, a budget is a statement of values,” the letter continues. “We believe that the level of resources your companies allocate to containing and combating online terrorist content is a reflection of the seriousness with which you are approaching this issue.”

The letter asks each company for its annual budget on counterterrorism; how many people work solely on counter-terrorism; and how many experts specialize in far-right extremism, foreign terrorist organizations including ISIS and Al Qaeda, and other types of extremism.

The letter gives a deadline of April 24, and is signed by Rep. Max Rose, who chairs the subcommittee on intelligence and counterterrorism, as well as Reps. Sheila Jackson Lee, Elissa Slotkin, and James Langevin.

“We’ve seen in graphic detail the extent that terrorist organizations and extremists have used social media to amplify their reach and message in recent years,” said Rose. “While social media companies tell us they’re taking this seriously, I want to see the numbers to back that up—and won’t stop until we get answers.”

A spokesperson for GIFCT did not immediately respond to a request for comment.