The FBI and U. S. Postal Service inspectors are investigating bogus official-looking letters sent to voters in at least 28 Florida counties questioning their citizenship and their eligibility to vote.

David Couvertier, a spokesman for the FBI in Tampa, said his office opened up an investigation into the possible attempt at voter intimidation on Wednesday after receiving reports that eligible voters throughout the state have received the letters.

“We’re taking it as a serious situation,” he said. “We’re looking at everything from civil rights violations to election fraud — to everything in between.”

Chris Cate, a spokesman for the Florida Secretary of State’s Office, said, “We believe these  letters appear to meet the standard of voter intimidation.” Between 50 and 100 such letters have been reported to state officials so far, “and those are only the ones we know about. We’re encouraging people to come forward.”

The fake letters, which first started showing up last Friday, have been sent under the names of real Florida county election supervisors — with some correct contact information — informing the voters that the supervisors have received “information” about their citizenship status, “bringing into doubt your eligibility as a registered voter.”