Senators raised the stakes against some of America’s biggest tech companies on Wednesday, telling them they must take more comprehensive action against foreign actors misusing their platforms. “You created these platforms ... and now they’re being misused,” Sen. Dianne Feinstein (D-CA) told the top lawyers at Facebook, Google, and Twitter. “And you have to be the ones who do something about it — or we will.”

Feinstein’s remarks came during a blistering hearing of the Senate Select Intelligence Committee, which has been investigating Russian meddling interference in the 2016 election. It is the second of three hearings at which representatives for Facebook, Google, and Twitter will speak, following yesterday’s appearance before a Senate Judiciary subcommittee.

Intelligence Committee Chairman Richard Burr (R-NC) began the meeting by warning fellow senators that the precise influence that Russian interference had in the 2016 election will likely never be known. “What we cannot do, however, is calculate the impact that foreign meddling and social media had on this election,” Burr said. “Nor can we assume that it must be the explanation for an election outcome that many people did not anticipate.”

“What we cannot do, however, is calculate the impact that foreign meddling and social media had.”

But senators dug in against tech companies with questions that, for the most part, were more detailed and sophisticated than those asked by their judiciary committee counterparts asked Tuesday. Feinstein, who attended yesterday’s hearing and asked questions at that hearing as well, expressed disappointment at the tech companies for answers that she said were vague and unsatisfying.

“I must say, I don’t think you get it,” Feinstein said. “You’re general counsels, you defend your company. What we’re talking about is a cataclysmic change. What we’re talking about is the beginning of cyber warfare. What we’re talking about is a major foreign power with the sophistication and ability to involve themselves in a presidential election and sow conflict and discontent all over this country.

“We are not going to go away, gentlemen,” Feinstein continued. “And this is a very big deal. I went home last night with profound disappointment. I asked specific questions, I got vague answers. And that just won’t do. You have a huge problem on your hands. And the US is going to be the first of the countries to bring it to your attention, and other countries are going to follow I’m sure. Because you bear this responsibility.”

“We are not going to go away, gentlemen.”

In an attempt to stave off federal regulation, the tech companies have announced plans to regulate themselves. Last month Mark Zuckerberg announced a nine-point plan for limiting foreign actors’ ability to influence elections, including new requirements that political ads be labeled and available for public inspection. Twitter announced it would build a “transparency center” where political ads bought on its platform can be publicly viewed.

Last month, a bipartisan group of senators introduced a bill, known as the Honest Ads Act, that would require new disclosures for online political advertising modeled on requirements for print and broadcast media. On Tuesday, one of the authors, Sen. Amy Klobuchar (D-MN) asked tech executives to commit to supporting her bill. None would. The bill still has just one public Republican supporter in the Senate.