DENVER (KDVR) — At least a dozen mail-in ballots in Mesa County were intercepted and sent in without the knowledge of the actual voters, Colorado Secretary of State Jena Griswold announced in a news conference Thursday. These ballots were filled out, signed and returned to a postal box. How many ballots have been cast in Colorado so far? Griswold said in the conference that the issue was initially discovered during the routine signature verification process. This is when ballots are looked at to make sure that the signature on them matches the one included in the registration. All ballots in the state undergo this verification process. How many ballots were affected? Two voters in Mesa County were contacted by the Mesa County Clerk and Recorder's Office to cure their ballots because the signatures did not match. Those voters informed the clerk's office that they had not actually sent in or even received a ballot yet. Ballot boxes open statewide as officials issue election reminders Another voter received a notification from BallotTrax that their ballot had been received by the clerk when they had not received their ballot in the mail yet. An investigation was then launched. Four fraudulent ballots had already been through the signature verification process. Three had already been counted but one was removed before it got to that point.  Griswold said that these votes cannot be removed from the count. This is because once a signature is verified, the ballot is separated from the signed envelope so the votes can be counted without knowledge of who cast it. Secretary Griswold said all victims will be given replacement ballots. Mesa County opens criminal investigation The clerk's office in Mesa County is currently reexamining every ballot envelope that has been received, and the investigation is ongoing. No suspects have been identified as of Thursday. Griswold said it was unknown how many people were involved. So far, the clerk's office has found that at least some of the ballots seemed to be signed by the same person. Mesa County Clerk Bobbie Gross released a statement after Secretary Griswold announced the incident. "I am fully committed to ensuring the integrity and security of our elections. We are currently investigating attempted election fraud," she said. "Our priority is to handle this investigation with the utmost care and diligence, and I believe that prematurely releasing details could compromise our ability to hold those responsible accountable. "While we understand the Secretary of State’s desire to make public statements, this is our community and our investigation," she said. Gross said it is "critical" that the office follow proper procedures so there is a "thorough and effective investigation without tipping off those involved." "The people of Mesa County deserve transparency and accountability," she said, "but it must be done in a manner that protects the integrity of the investigation." Hundreds of thousands of ballots across the state have already been returned ahead of Election Day on Nov. 5, with over 770,000 ballots being returned as of Thursday. In Mesa County, 27,625 ballots had been returned as of Thursday. Griswold: Colorado's elections are "safe and secure" Secretary Griswold said that elections in the state are still safe and secure, despite this incident. "This attempt at fraud was found and investigated quickly because of all the trailblazing processes and tools Colorado has in place like signature verification, ballot tracking, and the curing process," she said. "Every eligible Colorado voter will be able to make their voice heard this election.” Griswold encouraged people to sign up for BallotTrax, a free online service that allows Colorado voters to receive notifications about the status of their mail-in ballots. There is also the TXT2Cure system, where voters can use their phones to submit the information necessary to cure their ballots.