RALEIGH, N.C. (AP) -- Federal prosecutors investigating potential election crimes are digging into a North Carolina congressional race that's still undecided and being rerun this year after last year's contest was deemed tainted.

• Republican candidate Mark Harris and his campaign received subpoenas for documents, his personal attorney, David Freedman, said
• Harris isn't running in the new race that opened Monday with candidate filing that continues through Friday
• Party primaries are scheduled for May 14 with the general election in September

The state elections board on Tuesday provided a grand jury subpoena it received showing the U.S. Justice Department's Public Integrity Section in Washington, D.C., is conducting a criminal investigation. The subpoena demands that a grand jury receive documents related to an investigation into North Carolina's 9th Congressional District.

"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.

MORE: Full NC District 9 Coverage

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 election. Harris isn't running again in the race that opens with candidate filing this week.