Texas officials sent tens of thousands of delayed voter registration applications to county election officials this week after discovering an error, sparking a scramble to process them weeks out from the midterms.

The Texas secretary of state’s office told election officials last week that a problem with the Department of Public Safety’s system had been uncovered: Certain incomplete voter registration applications that were missing some information were not sent on to election officials, potentially leaving Texans unregistered or with out-of-date voter files. The nonprofit news outlet Votebeat was the first to report the problem.

State officials started transmitting the records on Tuesday. It’s unclear how many voters were affected, but large counties have reported tens of thousands of registration applications and updates that election officials must process in the less than a month before early voting begins on Oct. 19. And more applications are sure to pour in ahead of the Oct. 5 deadline to register to vote in Texas.

The state’s fourth-most populous county, Bexar, received more than 45,000 voter registration forms from DPS, and the fifth-most populous, Travis County, received more than 35,000.

“While that number may seem high, the Elections team is already hard at work reviewing every application and will be extending hours to make sure all records are updated well before early voting begins,” Bexar County Elections Administrator Michele Carew said in a statement.

Chris McGinn, the executive director of the Texas Association of County Election Officials, said he expected populous urban areas will be hit hardest, because there are more voter registrations to process and people in cities tend to move more often.

“There’s going to be a lot of counties that are paying a lot of overtime,” he said, speaking in a press briefing organized by the nonpartisan Center for Election Innovation and Research.

McGinn said some of the records may be duplicative — people may check the box to register to vote when they update their driver’s license, for instance — but still need time and attention from election officials.

Alicia Pierce, a spokesperson for the Texas secretary of state’s office, said a voter who does not appear on the state’s rolls but believes they registered to vote can cast a provisional ballot, and election officials can later search DPS records.

Texas is hosting several competitive statewide elections this fall. Democratic state Rep. James Talarico is facing off against Republican Attorney General Ken Paxton for a U.S. Senate seat. And Democratic state Rep. Gina Hinojosa is challenging GOP Gov. Greg Abbott.

In a statement, Talarico called the error “unacceptable” and urged Texans to check their voter registration online.

“Less than two weeks before the voter registration deadline, thousands of Texans are now in the dark about their voter registration status — even more aren’t aware of this error at all,” Talarico said. “This is what a broken, corrupt political system looks like: Texans follow the rules, register to vote before the deadline, and still risk losing their God-given right to the ballot box because their government failed to do its job.”

McGinn said voters might be better off calling their local registrar’s office. Texas’ online system has reportedly had problems this year, with some registrations inaccurately showing up as inactive.