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MIAMI (CBSMiami) — The House and Senate panels investigating Russian meddling in the 2016 U.S. presidential election were warned Wednesday that Moscow will do it again.

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Lawmakers heard more details about the cyber hacking and pressed current and former government officials about how to prevent future attacks.

Former Homeland Security Secretary Jeh Johnson told the House Intelligence Committee to expect more Russian cyber attacks.

“This is not just an academic exercise. This is a real threat,” said Johnson.

Johnson said figuring out how to tell American voters what Russian hackers were doing before Election Day was tricky.

“We were very concerned we not be perceived as taking sides in election. Injecting ourselves into a heated campaign,” said Johnson.

His department did alert the public and tried to help states after evidence revealed the Russians were infiltrating voter registration databases.

“State election officials are very sensitive about federal intrusion into their process,” said Johnson.

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States did accept help and DHS has designated election infrastructure as “critical.”

Johnson suggested Congress provide grants for states to tighten their cyber security protections and said raising awareness about hackers’ techniques could go a long way.

On the other side of the Capitol, Senators pressed DHS officials to identify the states hit in 2016.

Senator Mark Warner (D-VA) called for more transparency from the agencies.

“To not put all America on notice and know how many states hacked is just crazy,” said Warner. “I do not believe our country is made safer by holding this information back from the American public.”

“When an entity is the victim of a cyber incident, we believe very strongly in protecting the information around that victim,” said DHS Acting Deputy Undersecretary of Cybersecurity Jeanette Manfra.”I prefer not to go into those details in this forum. I can tell you that we are tracking 21 states.”

DHS said there was no evidence the 2016 voter ballots were altered.

Officials say they do extract the technical data related to the attacks and shares the information broadly.

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In addition to these two committees, Special Counsel Robert Mueller is also investigating Russian meddling and whether there was any collusion between President Donald Trump’s associates and Moscow. The president insists there was no collusion and has called the investigation a ‘witch hunt.’