The Board of Elections for Pennsylvania's sixth most populous county said Tuesday that a printing error on thousands of mail-in ballots made them unreadable, potentially delaying the results for a slew of primary races

Lancaster County officials said that when they opened the first batch of more than 21,000 mail-in ballots on Tuesday morning, they realized that "a significant number of the mail ballots did not scan." 

"Upon further inspection of the ballots, the county identified the ballots were printed by the mail ballot vendor, NPC, with the wrong identification code," the election officials explained. "This error prevents the ballots from being scanned on the county’s central scanners."

Election poll vote primary

A voter arrives to cast their mail-in ballot at the City-County Building in downtown Pittsburgh Monday, May 16, 2022.  (AP Photo/Gene J. Puskar)

Only about a third of the ballots were scanning properly. Both Democratic and Republican staff members will manually remark and tabulate the ballots with the wrong identification code. 

"Running fair and secure elections is a sacred trust," officials in the GOP-controlled county said. "The board of elections will do everything possible to ensure this problem is resolved in a transparent, secure way." 

TRUMP'S GOP CLOUT IS ON THE LINE IN PENNSYLVANIA'S REPUBLICAN SENATE PRIMARY

Officials blamed Act 77, a state law passed in 2019 that expands mail-in voting but prevents counties from opening the ballots until the morning of the election, making it impossible for them to foresee problems like they ran into Tuesday. 

election poll vote primary

Signs point the way for voters to cast their ballots at the polling location for the Pennsylvania primary election, Tuesday, May 17, 2022, in Harmony, Pa. (AP Photo/Keith Srakocic)

Voters in Idaho, Kentucky, North Carolina and Oregon were also hitting the polls on Tuesday. 

Election officials ran into a similar problem in Oregon's Clackamas County, where about half of the mail-in ballots had blurry bar codes that prevented them from being scanned. 

CLICK HERE FOR THE LATEST FOX NEWS MIDTERMS POWER RANKINGS

Pennsylvanians are voting on who will succeed retiring Republican Sen. Pat Toomey, a race that could have important implications for the balance of power in the Senate, as well as who will be the next governor of the state since Democratic Gov. Tom Wolf is prevented from running again by term limits. 

Mehmet Oz Pennsylvania primary Republican

Republican Senate candidate Mehmet Oz listens as former President Donald Trump calls into Oz's primary eve rally in Blue Bell, Pennsylvania on May 16, 2022 (Fox News )

The GOP primary in the Senate race is coming down to Dave McCormick, a former hedge fund executive and veteran; Kathy Barnette, a conservative commentator who is also a veteran; and Dr. Mehmet Oz, a celebrity physician who won former President Trump's endorsement. 

In the Democratic primary for the U.S. Senate seat, Lt. Gov John Fetterman was ahead in the polls and fundraising, but he remained in the hospital on Monday after suffering a stoke last week. 

CLICK HERE TO GET THE FOX NEWS APP

In the governor's race, Pennsylvania Attorney General Josh Shapiro will run uncontested on the democratic ticket. 

Republican voters, meanwhile, will have nine options on the ballot. Doug Mastriano, a retired U.S. Army colonel and state senator, is the frontrunner with Trump's endorsement

President Biden won Pennsylvania by 80,555 votes in 2020. 

The Associated Press contributed to this report.