PRAIRIE VIEW, Texas—Some students at a historically black university are wondering why an investigation by the office of Texas Attorney General Greg Abbott into alleged voting rights violations is still not finished.

Abbott’s office began its probe in December 2006 after allegations were made that about 300 students at Prairie View A&M University had to cast provisional ballots when their names were not on voting lists.

A provisional ballot is cast when someone shows up to vote and credentials for voting in a particular district cannot be verified on election day. Such a ballot is counted only after a voter’s eligibility is verified.

Local black leaders also contended that more than 1,000 voter-registration forms may not have been processed by Waller County officials.