Top officials at the FBI and Department of Homeland Security (DHS) have pushed back on claims from Sen. Bill Nelson Clarence (Bill) William NelsonDemocrats sound alarm on possible election chaos Trump, facing trouble in Florida, goes all in NASA names DC headquarters after agency's first Black female engineer Mary W. Jackson MORE (D-Fla.) that Russians have "penetrated" some of Florida's election systems.

In a letter to Florida election officials on Monday, DHS Secretary Kirstjen Nielsen Kirstjen Michele NielsenMore than million in DHS contracts awarded to firm of acting secretary's wife: report DHS IG won't investigate after watchdog said Wolf, Cuccinelli appointments violated law Appeals court sides with Trump over drawdown of immigrant protections MORE and FBI Director Christopher Wray said the two agencies have not observed the activity mentioned by the Democratic senator, but noted that Russian aggression is a real threat. ADVERTISEMENT

"Although we have not seen new or ongoing compromises of state or local election infrastructure in Florida, Russian government actors have previously demonstrated both the intent and capability to conduct malicious cyber operations," Nielsen and Wray wrote in a letter to Florida Secretary of State Ken Detzner (R), a copy of which was obtained by The Hill.

"DHS and the FBI will continue to notify any victim of a successful cyber intrusion into their election network in any jurisdiction nationwide," the letter stated.

Nielsen and Wray also emphasized the importance of their agencies' partnership with state election officials, saying "every local jurisdiction could be a potential target this election season, whether through malicious cyber operations or influence operations."

The letter from the two top intelligence officials comes just days after Nelson stood by his claim, which he first made earlier this month, that Russian hackers had successfully "penetrated" some of Florida's election systems ahead of the November midterm elections.

"Of course," Nelson told CNN last week when asked whether he still stands by his remarks.

NBC News, citing "three people familiar with the intelligence," reported last week that there was a classified basis for Nelson's claims. NBC reported that Nelson made the claims during a public event after he received information from the leaders of the Senate Intelligence Committee.

Despite the report, Nelson has not offered evidence publicly to support his claim nor have other lawmakers voiced support for his assertion.

Nelson has pointed to the letter he and Sen. Marco Rubio Marco Antonio RubioGOP lawmakers distance themselves from Trump comments on transfer of power McConnell pushes back on Trump: 'There will be an orderly transition' Graham vows GOP will accept election results after Trump comments MORE (R-Fla.) sent last month to Detzner, in which the two senators broadly warned state election officials about "cyber threats." But their letter did not mention current Russian infiltration in voting systems.

Senate Intelligence Committee Vice Chairman Mark Warner Mark Robert WarnerFBI director casts doubt on concerns over mail-in voting fraud Democrats call for declassifying election threats after briefing by Trump officials It's time to upgrade benefits MORE (D-Va.) and Rubio, a member of the Intelligence panel, both issued statements at the time of his remarks warning that the matter should not be politicized. Neither senator, however, directly said whether they agree with Nelson's remarks.

"This is not about politics. I urge officials at all levels of government to heed the warning and work with DHS and the FBI to address the threat," Warner said in a statement.

Still, Republicans are seizing on the remarks from Nelson, who is up for reelection this year. Republicans are running attack ads and demanding that the incumbent Democratic senator provide evidence to support his claims.