Federal authorities say they have not seen any "new or ongoing compromises" of state and local election systems by Russian hackers.
A joint letter sent Monday by the Federal Bureau of Investigation and the Department of Homeland Security comes after U.S. Sen. Bill Nelson said Russians had penetrated certain Florida county's election systems and "have free rein to move about" ahead of this year's election.
Federal officials earlier said Russian hackers targeted at least 21 states, including Florida, ahead of the 2016 election.
Gov. Rick Scott, Nelson's Republican rival in this year's elections, has pressed him for proof.
Scott issued a statement saying the agencies' letter shows Nelson was "irresponsible" and "reckless."