On Thursday, President Donald Trump insisted accusations of the Russians meddling in the 2016 election is a Democratic hoax. Although all he could offer as proof of his argument are his early morning rants on Twitter, investigators confirmed the hacking of state and local election databases.

Ken Menzel, general counsel of the State Board of Elections in Illinois, said over 90 percent of the almost 90,000 records filched by Russian hackers [VIDEO] included drivers’ license numbers, and 25 percent contained the last four digits of the Social Security numbers of voters.

Probers from Congress are now investigating if any of the private information stolen by the Russian hackers reached the Trump campaign.

The search for stolen data

Michael Bahar, the former top Democratic staffer on the House Intelligence Committee, said the heart of any investigation on the stolen data must find the answers to two key questions: firstly, how the data was stolen, and secondly, from whom it was stolen.

Since the Trump campaign is suspected of being involved in the Russian interference, the committee plans to have Brad Parscale, the digital director of the Trump campaign, testify in summer, according to CNN. To ensure no potential evidence are erased, in February, Capitol Hill probers asked the White House and law enforcement agencies to preserve all materials related to contacts between the Trump administration, the transition team, and campaign.

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Jeh Johnson’s testimony

Apparently, Trump's reference to his hoax accusation is the Wednesday testimony before Congress of former Homeland Security Secretary Jeh Johnson. The Democratic National Committee turned down an offer of help from the DHS, to identify the hackers and fix the vulnerabilities after the party’s email servers were hacked, Johnson disclosed.

In response to the president’s tweet, Adrienne Watson, the spokeswoman of the DNC, said the party has been in regular contact for many months with the FBI, and it will continue to cooperate with law enforcement on the investigation of the Russian meddling. Ex-White House Press Secretary Josh Earnest said the aim of Russia was to shake the confidence of the U.S. in holding an election. Had the Obama administration taken more active public steps to show worry over the initiatives by Russia, it would have been irresponsible, The Washington Post reported.

Current White House Press Secretary Sean Spicer he does not know if Trump believes the conclusion of 16 U.S. intelligence agencies which confirmed Moscow meddled in the 2016 election.