By David S. Cloud

Tribune Washington Bureau

WASHINGTON, D.C. — Lawmakers leveled blistering criticism at Facebook, Twitter and Google on Wednesday for failing to act aggressively to block Russian use of their social media platforms to sow division before and after last year’s presidential election.

The Senate Intelligence Committee hearing proved far more explosive than a similar hearing Tuesday by the Senate Judiciary Committee, with senators accusing the social media companies of permitting a flood of Russian-sponsored disinformation aimed at U.S. voters.

Sen. Richard Burr, a North Carolina Republican and chairman of the Intelligence Committee, said Russian authorities had secretly set up a Facebook account with 250,000 followers that promoted a May 2016 protest at a Houston mosque against “Islamization of Texas” — while another Russian account with 320,000 followers encouraged Muslims to attend a counterprotest.

Dozens of people from both sides showed up and the protests were covered by local news in Houston.

“People were brought together to foment conflict,” Burr told lawyers for Facebook, Google and Twitter. “Simply put, you must do better to protect the American people and frankly your users from this kind of manipulation.”

The social media giants have emerged as targets of multiple congressional inquiries into Russian interference in last year’s election after the companies found that groups backed by Russia posted ads and other content that reached tens of millions of American voters.

U.S. intelligence agencies have concluded that the “influence campaign” was aimed at undermining U.S. democracy and helping Donald Trump beat Hillary Clinton in the election.

Sen. Dianne Feinstein, D-Calif., warned the California-based companies that they needed to be more aggressive at stopping secret foreign use of their technology — or Congress would step in.

“You bear this responsibility. You created these platforms and now they are being misused,” she said. “You have to be the ones to do something about it or we will.”

A day after telling the Judiciary Committee that 126 million Americans may have seen Russian-linked ads and posts on Facebook-owned platforms since 2015, Colin Stretch, the company’s general counsel, raised the estimate Wednesday to “a little less than 150 million” Americans, or nearly half the U.S. population.

He said the company had discovered an additional 120,000 Russian-linked posts on Instagram, which is owned by Facebook.

Republicans noted that Russian efforts were not limited to attacking Clinton and supporting Trump.

Sen. Susan Collins, R-Maine, said her state’s Republican governor, Paul LePage, was accused of being a white supremacist in posts on a Russian-linked Facebook account targeting African-Americans in August 2016.

“It is not a secret that American is the country of white supremacists and people like LePage must be replaced,” one post said, according to Collins.

A year later, in August 2017, another Russian-created Facebook page called “Being Patriotic,” praised LePage and warned he was under threat from political opponents, saying “even the governor is not safe from leftist haters,” according to Collins.

Trump has repeatedly dismissed the claims that Russian intervened in the 2016 election as a “hoax,” and has called the congressional investigations and a separate criminal investigation a “witch hunt.”

Under questioning from New Mexico Democratic Sen. Martin Heinrich, Stretch conceded that the Russian effort was real, saying the ads on Facebook were “not a hoax.”