Maricopa County Recorder's Office acknowledged Sunday that a third-party vendor "mistakenly" mailed out 3,126 ballots prematurely but said the incident affected "only the timing of the mailing."

"The correct ballots were mailed to the correct voters," the office said on social media. "Upon consultation with the Maricopa County Attorney's Office, it was determined that the ballots remain valid and do not need to be voided or reissued."

The office said it was notified Friday of the incident, which occurred Thursday. The vendor has been identified as Runbeck Election Services.

The mailing occurred six days before the scheduled Oct. 7 mail out date. Midterm Election Day is Tues., Nov. 3. 

"Voters may complete and return them normally," the Recorder's office also said in a social media post. 

Any ballots received before early voting begins will remain unopened and securely stored until processing begins and no voters were adversely affected, the office also said.