QUINCY, Ill. (AP) – A computer coding error is forcing a western Illinois election authority to recount about 2,000 ballots cast during early voting.

Adams County will send the ballots through the voting machine again on Thursday night. The Illinois State Board of Elections will have someone observe the recount. Representatives of both the Democratic and Republican counties are invited as well.

Adams County Clerk Chuck Venvertloh tells The Quincy Herald Whig that the error was found during a test and state election board technicians helped his office fix the problem. Venvertloh says the error only affected the federal ballot. State board of elections general counsel Ken Menzel says a tabulator wasn’t recording the proper volume of ballots.

State elections officials say coding errors aren’t uncommon and are identified during pre-election testing.