A top FBI counterterrorism official said Wednesday that he has seen a major change in social media companies’ willingness to address extremist content on their platforms.

“We are seeing a tide change in social media companies being more proactive policing their own,” Michael McGarrity, the FBI’s assistant director for counterterrorism, said at a House Homeland Security Committee hearing.

“And when they see something that is noteworthy and alarming beyond First Amendment, they will give us leads,” McGarrity added.

The FBI official asserted that social media companies were not “self-identifying content” to the same degree a few years ago, and they are currently facing a “learning curve” in how best to handle it.

His remarks came as the House panel, which has been led by Democrats since January, held its first hearing on domestic terrorism in years. The hearing focused heavily on the role of social media companies in dealing with incendiary and hateful content, with lawmakers signaling a desire to hold the companies “accountable” when they do not address domestic terrorists on their platforms.

McGarrity testified alongside Brian Murphy, the Department of Homeland Security’s (DHS) principal deputy undersecretary for intelligence and analysis, and Brad Wiegmann, the deputy assistant attorney general of the Department of Justice’s (DOJ) national security division.

Each of the witnesses emphasized that government’s limited power to address content from Americans, even when it is extreme or hateful. They said that tech companies have more room to deal with the issue because social media giants like Facebook and Twitter are not held to the First Amendment and police their platforms according to community guidelines.

“When you’re talking about extremist content online, the First Amendment does impose some significant constraints,” Wiegmann from the DOJ told the committee.

“We are prohibited from reviewing, looking at First Amendment activity,” McGarrity added.

But the government can partner with social media companies such as Facebook, Twitter and Google in a limited capacity, the witnesses told lawmakers.