Florida voters receive letters saying their citizenship is being challenged, along with their eligibility to vote.
Florida's Collier County Supervisor of Elections office is investigating complaints of voter intimidation.
Four registered voters have received form letters challenging their citizenship and eligibility to vote.
The letters, mailed from Seattle, Washington, have been turned over to the FBI.
It's unclear who sent them.
There's no connection between the Collier County residents who received them, other than they are all registered Republicans.
Tim Durham with the Collier County Supervisor of Elections Office says none of the victims names match earlier inquiries regarding citizenship.
Election supervisors consider the letters threatening because they say trying to vote could lead to an arrest or even prison.
Durham says that a real letter from the office would not contain such verbiage.
"This to me though seems very strong language and the intent of this is to keep people from going to the polls and voting," he said.
Florida Secretary of State Ken Detzner sent a letter to all county supervisors of elections, warning of the scam that has appeared in "multiple counties."
Lee County Elections Supervisor Karen Harrington says two such letters have been reported to her by Lee County voters, but she had yet to see them.