Due to a problem with the state’s breath-testing equipment, approximately 3,500 people accused of drunken driving will have their licenses returned.

According to The Oklahoman, the former director for the state’s Board of Tests, McBeth Sample Jr., switched the nameplate on a piece of testing equipment, which allowed the use of an unapproved machine that calibrates breath testing devices.

“The department looked at it, and we are uncomfortable with how and what was done, and why it was done without the approval of the board,” Department of Public Safety attorney Wellon Poe told The Oklahoman. “We’re not challenging the legality, we’re just not comfortable with how it was done by the Board of Tests.”

Sample was subsequently fired after the error was discovered.

Because of the use of the unapproved device, Department of Public Safety officials told The Oklahoman that they were concerned about the test results holding up as evidence in a court case.

Although the licenses will be returned, the drivers involved can still be prosecuted for their alleged crimes, minus the loss of their licenses, lawyers told The Oklahoman.