A federal grand jury is examining allegations of ballot fraud in a North Carolina congressional race, issuing subpoenas this month that represent the first public evidence that U.S. prosecutors are investigating the matter.

Officials with the North Carolina State Board of Elections and a lawyer for former Republican congressional candidate Mark Harris confirmed Tuesday that they had received subpoenas from the Justice Department’s Public Integrity Section seeking all documents related to allegations of election fraud in the 9th Congressional District.

Leslie McCrae Dowless, the GOP political operative hired by Harris in last year’s election, also received a subpoena, according to Charlotte television station WBTV.

A Justice Department spokeswoman declined to comment.

Last month, a local prosecutor in Raleigh indicted Dowless on seven state felonies, including obstruction of justice and possession of absentee ballots.

The federal subpoenas come less than a month after state election officials tossed the November results in the 9th District after finding that Dowless orchestrated a “coordinated, unlawful, and substantially resourced absentee ballot scheme” last year to illegally collect, forge and possibly discard other voters’ mail-in ballots.

Officials also accused Dowless of hiding evidence of the operation as it unfolded and obstructing the state’s investigation after the election.

State election officials first referred evidence of ballot fraud in the 9th District to the U.S. attorney in the Eastern District of North Carolina in January 2017, nearly two years before allegations roiled Harris’s race against Democrat Dan McCready last fall. Frustrated state investigators said that they saw little evidence that prosecutors were pursuing the case.

A spokesman for the office did not immediately respond to a request for comment on why the subpoenas were sought by the Justice Department in Washington and not the U.S. attorney in Raleigh, Robert J. Higdon Jr.

Complicating matters is the fact that one of Harris’s sons, John, is an assistant U.S. attorney in Higdon’s office.

Last month, John Harris testified at a state elections board hearing that he had warned his father that he believed Dowless employed illegal tactics to collect absentee ballots. Two individuals with knowledge of the investigation said John Harris is likely to be called as a witness in the federal case.

Mark Harris has denied knowledge of the scheme. For weeks after the election, he insisted that his 905-vote victory entitled him to be seated in Congress. That changed after state officials heard public evidence of the ballot scheme at last month’s hearing, prompting Harris to say he believed that fraud had tainted the outcome. The following week, Harris said he would not run in the special election scheduled for later this year.

Kim Westbrook Strach, executive director of the state elections board, applauded the news of federal subpoenas.

“We support the efforts of state and federal authorities to investigate and prosecute crimes against the elections process,” Strach said in a statement Tuesday. “State Board staff are compiling records responsive to the federal grand jury subpoena and are prepared to assist federal and state prosecutors in their investigations. We hope that prosecutions in these cases will help restore voters’ confidence in our elections and serve as a strong deterrent to future elections fraud.”