A $10,000 reward is on offer after a murderer escaped from jail with a prison officer – with authorities investigating “if something else was going on”.

Casey Cole White left a detention centre in Florence, Alabama, with assistant director of corrections Vicky White on Friday morning.

The pair – who are not related – were apparently heading to a nearby courthouse but disappeared.

Authorities said Ms White, who was armed at the time, was “missing and endangered” and had broken the rules by being alone with the inmate.

Lauderdale County Sheriff Rick Singleton said they were also looking at previous contact to “see if something else was going on” between the two.

Mr Singleton said the 56-year-old had handed in her retirement papers the day before, and claimed she was taking White for a mental health evaluation at the court – despite one not being scheduled.

The vehicle they were travelling in was found at a shopping centre car park, but no one realised they were missing for about six hours.

Calls to Ms White’s phone have reportedly been going to voicemail.

“Casey White is believed to be a serious threat to the corrections officer and the public,” said US marshal Marty Keely.

The 38-year-old was serving a capital murder charge, with local media saying he had confessed to a 2015 stabbing death while jailed for other crimes in 2020.

People are warned not to approach White, who is described as 6ft 9in (2.06m) and about 260lbs (18 stone 8), with brown hair and hazel eyes.