Republican National Committee Chairman Reince Priebus said Friday the FBI's decision to reopen its investigation of Hillary Clinton's private server is a "stunning development," claiming the new emails investigators found must be "serious."

"The FBI's decision to reopen their criminal investigation into Hillary Clinton's secret email server just eleven days before the election shows how serious this discovery must be," Priebus said in a statement.

"This stunning development raises serious questions about what records may not have been turned over and why, and whether they show intent to violate the law," he added.

FBI Director James Comey announced in a letter to congressional committee chairs on Friday that the agency had uncovered new emails "pertinent to the investigation" into Clinton's unsecured server and would "take appropriate investigative steps designed to allow investigators to review these emails to determine whether they contain classified information."

Upon conclusion of the FBI's year-long investigation into Clinton's emails earlier this summer, Comey had recommended that the Justice Department forego pursuing criminal charges against the former secretary of state. He cited insufficient evidence of criminal intent on Clinton's behalf.

RNC spokesman Michael Short reacted to the news on Friday by calling on reporters to ask down-ballot Democrats whether they will continue to support Clinton for the remainder of the election in light of the FBI surprise.

The Democratic National Committee has yet to comment on the latest development involving the FBI investigation into Clinton's private email server.