US police are searching for an escaped inmate who is facing murder charges, and a guard who disappeared with him.

Inmate Casey White and corrections officer Vicki White were last seen on Friday morning at the Lauderdale County Sheriff's Office in Alabama.

Ms White said she was taking him to a mental evaluation, but officials later realised it had not been scheduled.

Authorities are investigating whether Ms White helped the inmate escape, or if she was taken hostage by him.

Despite their matching surnames, the pair are not related. Authorities say Casey White should be considered "armed and extremely dangerous" - in part because he may now have access to the officer's gun.

Speaking at a press conference on Friday, Lauderdale County Sheriff Rick Singleton said Ms White left the detention centre with the prisoner at about 09:30 CDT (15:30 BST) after telling colleagues she was going to drop him off at the courthouse for a mental health evaluation.

She said she would then get some medical attention because she was not feeling well, Sheriff Singleton added.

Shortly after 11:00 someone found her vehicle in a shopping centre car park.

At about 15:30 officials realised the prisoner had not been returned to custody, and no one could contact the officer.

The US Marshals Service is offering a reward of up to $10,000 (£7,950) for information leading to Casey White's recapture and the location of Vicki White.

"Casey White is believed to be a serious threat to the corrections officer and the public," US Marshal Marty Keely said in a statement.