Several Alabama voters - including candidate Mo Brooks - found themselves listed as inactive when they arrived at the polls today to cast their ballots in the U.S Senate primary.

Brooks - one of 10 Republicans seeking the GOP nomination for the U.S. Senate - discovered he was listed as "inactive" on voter registration lists when he arrived to cast his ballot in Huntsville this morning.

He wasn't the only one.

Alabama Rep. Patricia Todd, a Birmingham Democrat, said she was also listed as inactive.

"This is screwed up! The (Secretary of State's) office said they sent out postcards to every voter, I never got one and neither did my wife. I asked several other folks and they never received one," Todd wrote on Facebook. "Don't let them keep you from voting! You can vote even if you are inactive."

Alabama Secretary of State John Merrill confirmed anyone listed on the inactive list can still cast a ballot after they provide updated information.

"Being inactive does not affect an individual's ability to vote if they update their information which they can do on Election Day," Merrill said.

From January to March of this year, the Alabama Secretary of State's office mailed postcards to registered voters in Alabama. The first postcard was non-forwardable and was sent to the last known address of the voter. If it was successfully delivered, no other action was taken.

If it was returned as undeliverable, a second forwardable notice was sent to the person's last-known address. The second notice required the voter to confirm their address. If the second card was returned as undeliverable, the person was placed on the inactive list.

An inactive voter is still eligible to vote after filling out an updated form at the polling place. At that point, a voter is considered "active". If a voter on the inactive list does not vote during the next two federal election cycles, they can be removed from registration lists.

In Brooks and Todd's case, the U.S. Postal Service failed to deliver the cards, Merrill said.