A report prepared for the Senate Intelligence Committee's probe into Russia's online disinformation campaigns aimed at U.S. voters accused Facebook, Google and Twitter of impeding the investigation.

The analysis, prepared by researchers with the firm New Knowledge, said the internet giants submitted incomplete datasets to the panel and may have misled lawmakers about the efforts of the Russian troll farm known as the Internet Research Agency.

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"Regrettably, it appears that the platforms may have misrepresented or evaded in some of their statements to Congress; one platform claimed that no specific groups were targeted (this is only true if speaking strictly of ads), while another dissembled about whether or not the Internet Research Agency created content to discourage voting (it did)," the report said. "It is unclear whether these answers were the result of faulty or lacking analysis, or a more deliberate evasion."

The Washington Post was first to report on the document, which was one of two third-party analyses submitted to the panel on the Internet Research Agency's efforts to sow discord among U.S. voters during and after the 2016 campaign. The other was conducted by researchers at the University of Oxford and the digital analytics firm Graphika.

Both reports concluded that the Internet Research Agency sought to promote President Trump Donald John TrumpBiden on Trump's refusal to commit to peaceful transfer of power: 'What country are we in?' Romney: 'Unthinkable and unacceptable' to not commit to peaceful transition of power Two Louisville police officers shot amid Breonna Taylor grand jury protests MORE and the Republican Party.

"What is clear is that all of the messaging clearly sought to benefit the Republican Party — and specifically, Donald Trump," the Oxford report said.

A Facebook spokesperson said in a statement that the company has been fully cooperative with the Russia probe.

"We've provided thousands of ads and pieces of content to the Senate Select Committee on Intelligence for review and shared information with the public about what we found," the spokesperson said. "Since then, we've made progress in helping prevent interference on our platforms during elections, strengthened our policies against voter suppression ahead of the 2018 midterms, and funded independent research on the impact of social media on democracy.”

A spokesperson for Twitter said in a statement: “Our singular focus is to improve the health of the public conversation on our platform, and protecting the integrity of elections is an important aspect of that mission. We’ve made significant strides since 2016 to counter manipulation of our service, including our release of additional data in October related to previously disclosed activities to enable further independent academic research and investigation.”

A spokeswoman for Google declined to comment but pointed to the company's efforts to cooperate with the Senate probe and improve transparency for its political ads.

Led by Sens. Richard Burr Richard Mauze BurrRep. Mark Walker says he's been contacted about Liberty University vacancy Overnight Defense: Trump rejects major cut to military health care | Senate report says Trump campaign's Russia contacts posed 'grave' threat Senate report describes closer ties between 2016 Trump campaign, Russia MORE (R-N.C.) and Mark Warner Mark Robert WarnerDemocrats call for declassifying election threats after briefing by Trump officials It's time to upgrade benefits Intelligence chief says Congress will get some in-person election security briefings MORE (D-Va.), the Senate Intelligence Committee has been investigating Russia's election interference for almost two years.

Much of the investigation has taken place behind closed doors, with lawmakers and committee staff interviewing witnesses including Donald Trump Jr. Don John Trump'Tiger King' star Joe Exotic requests pardon from Trump: 'Be my hero please' Zaid Jilani discusses Trump's move to cancel racial sensitivity training at federal agencies Trump International Hotel in Vancouver closes permanently MORE and Michael Cohen, the president's former personal attorney who recently pleaded guilty to lying to Congress about discussions about plans to build a Trump property in Moscow.

Some of the investigation has taken place publicly, including the dramatic testimony of former FBI Director James Comey James Brien ComeyDemocrats fear Russia interference could spoil bid to retake Senate Book: FBI sex crimes investigator helped trigger October 2016 public probe of Clinton emails Trump jabs at FBI director over testimony on Russia, antifa MORE last summer and, later, public hearings with top tech company executives.

Warner has repeatedly expressed frustration with Silicon Valley throughout the process and has proposed a number of ways to regulate the internet platforms.

"This should stand as a wake up call to us all that none of us are immune from this threat, and it is time to get serious in addressing this challenge," Warner said in a statement Monday. "That is going to require some much-needed and long-overdue guardrails when it comes to social media. I hope these reports will spur legislative action in the Congress and provide additional clarity to the American public about Russia’s assault on our democracy.”

The committee has already released investigative reports on election security and the intelligence community's assessment of Russian interference. Lawmakers are expected to unveil their own reports on social media, the Obama administration's response to Russian meddling, and whether there was collusion between the Trump campaign and Moscow.

Burr has signaled the investigation will extend into 2019, telling The Hill last week that he is “fairly confident” the probe will wrap up in the spring.

Monday's report found that Russia used a myriad of social media tools and messages to promote President Trump's 2016 campaign and his administration.

Researchers said the Internet Research Agency emphasized an "expansive cross-platform media mirage" to target black voters.

When its Facebook campaign attracted attention from lawmakers and the special counsel's office, the group shifted many of its resources to Instagram, which is owned by Facebook.

Among Trump supporters, the group pushed the unsupported claim that the president would have won the popular vote if it weren't for undocumented immigrants flooding the polls. The campaign also targeted liberals with an array of messages, pushing back against early calls for impeachment and attacking the Electoral College.

"Increasingly, we’ve seen how social media platforms intended to foster open dialogues can be used by hostile foreign actors seeking to manipulate and subvert public opinion," Burr, who chairs the Senate Intelligence Committee, said in a statement.

"This newly released data demonstrates how aggressively Russia sought to divide Americans by race, religion and ideology, and how the [Internet Research Agency] actively worked to erode trust in our democratic institutions. Most troublingly, it shows that these activities have not stopped."

Updated at 1:17 p.m.