IOWA CITY, Iowa (AP) — A Republican candidate seeking to flip a Democratic-held Iowa congressional seat pulled ahead by 49 votes Tuesday after a county discovered that it failed to report accurate results from a small town on election night.

The dramatic turn was the latest in the seesawing race between Republican Mariannette Miller-Meeks and Democrat Rita Hart, and it may not be the last.

The 24 counties in the southeastern Iowa district were certifying their votes Tuesday after completing their official canvasses. It’s possible additional provisional ballots or absentee ballots that arrived by Monday at noon could be added to some county totals.

The race is considered among the closest in the nation and could remain unsettled for weeks.

Lucas County Auditor Julie Masters said she discovered Monday that the results for a precinct in the town of Russell, population 500, had not been reported accurately on Election Night. She said test results in the software used for reading machine cartridges were reported instead of the actual results, which were 217 votes for Miller-Meeks and 54 for Hart.

“The machine did not lead us down the wrong path,” she said at a news conference in Chariton. “Through human error, we didn’t get all the results reported correctly.”

The change erased Hart’s slim lead. By mid-day Tuesday, Miller-Meeks was leading by 49 votes out of more than 394,000 cast as other minor adjustments from counties trickled in as they certified their totals. Miller-Meeks had 196,816 votes while Hart had 196,767.

Iowa Secretary of State Paul Pate ordered Lucas County to conduct a machine recount of all of its votes, and a hand recount for the precinct in question. He said that process would begin Thursday.

“We want to make sure we get it right,” he said.

Hart’s campaign manager Zach Meunier expressed anger at the situation in Lucas County, where the board quickly certified the corrected results.

“It is outrageous that Lucas would identify a race defining change in the middle of the night the night before the county canvass, six days after the election, and then rush to certify results just hours later before accuracy has been ensured,” he said.

He called on all counties to take special care to ensure their totals are correct, warning: “Anything less will perpetuate doubt around this election.”

Pate said the county’s certified totals would be amended if the recounts change them.

The race appears headed for a much wider recount in any event. The winner must be certified by Nov. 30 by a panel of top state officials.