TALLAHASSEE, Fla. -

Thousands of former convicts in Florida who had their voting rights restored over a four-year period may not know they are eligible to cast a ballot this year, the American Civil Liberties Union said on Wednesday.

The group said it checked state records and discovered that the state was unable to let nearly 18,000 former prison inmates know their rights had been restored. Instead the notices were returned by postal authorities as undeliverable.

The ACLU also said that current voting records show that three-quarters of those on the list are not currently registered to vote.

Howard Simon, executive director of the ACLU of Florida, criticized the state for not doing more to find people who are now eligible to vote. And he contrasted it with recent efforts by Gov. Rick Scott and the Florida Legislature to cut back on early voting days and to make it harder for groups to register voters.

Simon questioned whether the Scott administration would do anything to reach out those people who may be eligible to vote. Scott has also pushed a contentious plan to find potentially ineligible voters on the rolls and remove them.

But it turns out that the notices to former convicts were sent out primarily when former Gov. Charlie Crist was in office.

Convicted felons who leave prison are ineligible to vote unless their rights are restored by the state.

Crist in 2007 pushed to restore rights automatically to felons convicted of non-violent crimes. Those rights include voting, serving on a jury, holding public office and holding certain jobs requiring licenses, such as alarm system contractors and dental hygienists.

Scott and members of the Cabinet ended the policy in March 2011 and felons must now wait at least five years before they can apply to have their rights restored.

It was during this time period that the notices, or certificates of rights restoration, were returned as undeliverable to the Florida Parole Commission.

Tammy Salmon, a spokeswoman for the commission, said the state had a set of addresses it received from the state's prison system but they didn't have any other addresses where it could send the certificates.

"We don't have a way to reach a person," she said.

Salmon, however, pointed out that anyone who has applied for rights restoration can find out about their status by going to a state-run website: flrestoremyrights.com.