(AP) — About 16,000 voters in Nebraska will receive letters next week asking for additional information in an effort to update their registrations.

The recipients will be asked to provide their driver’s license numbers and the last four digits of their Social Security number. Secretary of State John Gale says the data will be added to information that is already on file.

Gale says the request is part of its routine list maintenance, and compliance is voluntary. He says the information improves the accuracy and security of the state’s registration database.

Gale says many of the 16,000 voters submitted their registrations before 2003, when Social Security information and driver’s license numbers were first required in Nebraska as part of the Help America Vote Act.