Get breaking news alerts and special reports. The news and stories that matter, delivered weekday mornings.

RALEIGH, N.C. — Federal prosecutors investigating potential election crimes have demanded documents for a grand jury reviewing a North Carolina congressional race that's still undecided and being rerun after last year's contest was deemed tainted.

The state elections board on Tuesday provided a grand jury subpoena issued last week showing the U.S. Justice Department's Public Integrity Section in Washington, D.C., is conducting a criminal investigation. The subpoena demands "all documents related to the investigation of election irregularities affecting counties within the 9th Congressional District."

The scandal represents a rare case of a federal election redone because of fraud.

Let our news meet your inbox. The news and stories that matters, delivered weekday mornings. This site is protected by recaptcha

"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," state elections director Kim Westbrook Strach said in a statement Tuesday.

The elections board heard evidence last month that a political operative working for Republican candidate Mark Harris in rural Bladen County collected mail-in ballots, making votes vulnerable to being changed or discarded. The elections board ordered a new contest for the district, which includes part of Charlotte and extends eastward along the South Carolina border almost to the Army's Fort Bragg.

Harris isn't running in the new race that opened Monday with candidate filing that continues through Friday. Democrat Dan McCready is running again after what appeared to be a narrow loss in November's election. Party primaries are scheduled for May 14 with the general election in September.

Harris' campaign and his former political operative, Leslie McCrae Dowless Jr., also received grand jury subpoenas, WBTV in Charlotte reported. Harris' attorneys and the spokesman for his 2018 campaign didn't respond to messages from The Associated Press on Tuesday. Neither did Dowless and his attorney.

Dowless and four people he allegedly hired to collect ballots were charged in state court last month on felony charges, including possessing absentee ballots related to their work in the 2016 primary and general elections and last year's GOP primary. The district attorney prosecuting the case said she also is investigating potential crimes leading up to the 2018 general election.

Dowless' state charges involve a similar ballot-collection scheme that the elections board uncovered in late 2016 and notified the U.S. attorney's office. Since then, federal prosecutors based in Raleigh have given no public indication they did anything about warnings from Strach that her office found "that individuals and potentially groups of individuals engaged in efforts to manipulate election results through the absentee ballot process."

"The evidence we have obtained suggest that these efforts may have taken place in the past and if not addressed will likely continue for future elections," Strach wrote to the acting U.S. attorney in January 2017.

Spokesmen for the Justice Department in Washington and the U.S. attorney's office in Raleigh refused to explain why the agency's Public Integrity Section has taken on the 9th District case. The section is responsible for combating corruption by public officials and supervises the investigation and prosecution of election crimes.

The elections board's subpoena demands the documents in time for three days of grand jury proceedings starting April 16.