DES MOINES, Iowa (AP) — Errors in Iowa’s list of felons cost at least 20 people the right to vote in November’s midterm elections, and officials have known about problems in the list since 2012, according to a newspaper investigation of six counties’ records.

The list of roughly 69,000 people who aren’t allowed to vote wrongly includes some people who were charged but not convicted of a felony and some who received a deferred judgment, which means their records were expunged after they completed probation, the Des Moines Register reported .

The American Civil Liberties Union, NAACP and other civil rights groups say they are worried. “This is a concern we’ve had for a while, that the list itself is not accurate,” said Daniel Zeno, policy director for the ACLU of Iowa. Jessica Bensley said she didn’t learn she was on the list until her ballot was rejected in November, but Bensley has never been convicted of a felony.

“Why was I not contacted telling me my voter’s rights were being taken away?” Bensley asked. Iowa agencies blame each other for the problems in the list. The Secretary of State’s office has urged county auditors to verify each felony conviction before rejecting a ballot, but the auditors say that’s not possible with their resources.

In 2012, the Iowa Division of Criminal Investigation reviewed several ballots that were rejected because voters’ names were on the state’s felon list. Cerro Gordo County Auditor Kenneth Kline said in a memo to then-Secretary of State Matt Schultz that having an experienced investigator with access to state databases was important in verifying voting rights.