The FBI and local police are investigating how at least 19 dead Virginians were recently re-registered to vote in this critical swing state.

One case came to light after relatives of a deceased man received a note congratulating him for registering, Rockingham County Commonwealth’s Attorney Marsha Garst said Thursday.

“His family members were very distraught,” said Garst, who confirmed the existence of the FBI and police investigation but said she could provide few details because the case is ongoing.

All 19 were initially registered as voters in the Shenandoah Valley city of Harrisonburg, although a clerk double-checking the entries later raised questions about one. She recognized the name of Richard Allen Claybrook Sr., who died in 2014 at age 87, because his son is a well-known local judge. She happened to recall that the judge’s father had died.

“He was a retired Fairfax County elementary school principal and had fought in World War II,” said his son, retired Harrisonburg General District Court Judge Richard Allen Claybrook Jr. “So our family is very disgusted that they would pick his name, because he was such a law-abiding citizen devoted to public service.”

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All of the forms had been submitted by a private group that was working to register voters on the campus of James Madison University, according to the Harrisonburg registrar’s office. The group was not identified. No charges have been filed.

Republicans in the state House of Delegates, who in recent years have supported tighter voter ID laws, held a conference call with reporters to call attention to the investigation.

“Oftentimes we hear our Democratic colleagues suggest that voter fraud doesn’t exist in Virginia, or it’s a myth,” House Speaker William J. Howell (R-Stafford) said. “This is proof that voter fraud not only exists but is ongoing and is a threat to the integrity of our elections.”

House Minority Leader David J. Toscano (D-Charlottesville) said the case was not proof of voter fraud because no one had actually managed to cast a vote in the names of the dead.

“First of all, there was no voter fraud — they caught him,” Toscano said. “Nobody cast a vote. . . . There’s still no evidence of that going on in the state. But there is evidence every time you turn around that the Republicans are trying to make it more difficult for citizens to vote in elections.”