WASHINGTON (AP) — Lawmakers demanded answers Wednesday from leading social media companies about why they haven't done more to combat Russian interference on their sites, and said congressional action might be needed in response to what one Democrat called "the start of cyberwarfare" against American democracy.

Representatives from Facebook, Twitter and Goggle struggled at times to defend themselves against complaints they didn't act quickly or thoroughly enough as it became evident that Russians used the sites to try and influence the 2016 U.S. election.

The top Democrat on the Senate Intelligence Committee said his questions about the interference were "blown off" by the companies until this summer.

"Russia's actions are further exposing the dark underbelly of the ecosystem you have created," said Virginia Sen. Mark Warner as Congress held a second day of hearings on the issue.

The House Intelligence Committee planned an afternoon hearing as part of the Capitol Hill investigation into Russian meddling in the election and whether it was linked to Donald Trump's campaign.

The companies faced questioning Tuesday from the Senate Judiciary Committee.

The message was clear from a Democrat on both those Senate committees: Do more or Congress will.

"I must say I don't think you get it," said California Sen. Dianne Feinstein. "What we're talking about is a cataclysmic change. What we're talking about is the start of cyberwarfare ... We are not going to go away, gentlemen."

The companies disclosed new details this week about the election interference. Facebook said Russia-linked ads reached as many as 126 million people. Twitter said it uncovered and shut down 2,752 accounts linked to a Russian agency, nearly 14 times as many as it handed over to congressional committees three weeks ago.

Sen. Richard Burr, chairman of the Senate Intelligence Committee, warned against jumping to conclusions that the Russian interference on social media platforms was designed to help one candidate or another.

"This is an incredibly complex story," said Burr, R-N.C. He added: "We do better when you do better."

Facebook has turned over more than 3,000 ads it found on the site that are linked to Russia's Internet Research Agency. They have not yet been released, but Burr revealed some details in an attempt to rebut reports that they were targeted to contested states such as Michigan and Wisconsin close to the November 2016 election.

Burr said more ads were targeted toward Maryland, a solidly Democratic state. Many ads were also targeted to New York, which Democrat Hillary Clinton won, and Missouri, carried by Republican Trump. Most of the geographically targeted ads ran in 2015, before the primaries were decided, he said.

Burr showed photos of events in Texas that were organized by one of the Russian pages called "Heart of Texas." He noted that some who attended the events said they noticed that no one from the organizing group was there.

Warner pressed Facebook's general counsel, Colin Stretch, on whether the company had cross-referenced accounts taken down during the French election this year to see if they corresponded to any of the Russia-linked accounts that operated in the U.S.

Warner said he found it "disappointing" when Stretch could not answer whether they had.

He also asked Stretch why Facebook delayed taking down an account that purported to be linked to the Tennessee Republican party.

"That was an absolute miss," Stretch said.

Facebook said Monday that the Russia-linked accounts generated 80,000 posts on 120 pages between January 2015 and August 2017. Possible views reached the millions after people liked the posts and shared them. Those are separate from the 3,000 ads the committee turned over to the committees.

Twitter said its Russia-linked accounts put out 1.4 million election-related tweets from September through Nov. 15 last year — nearly half of them automated. The company also found nine Russian accounts that bought ads, most of which came from the state-backed news service RT, previously known as Russia Today.

Google said it found evidence of "limited" misuse of its services by the Russian group, as well as some YouTube channels that were likely backed by Russian agents.

During Tuesday's hearing, none of the companies would commit to fully supporting legislation proposed by Warner and Sen. Amy Klobuchar, D-Minn., that would bring political ad rules from TV, radio and print to the internet.

Klobuchar dismissed pledges from the companies this week to be more transparent about political ads, calling that an unenforceable "patchwork" of self-policing. The companies have put new measures in place for election ads, though they have done less to address the issue ads that were found after 2016.