A woman has been beheaded by her co-worker at a US food distribution centre.

Police sergeant Jeremy Lewis said the woman, who has not been identified, was killed by a man who attacked her and another woman at Vaughan Foods in Moore, Oklahoma City.

An off-duty officer who was working at the business shot the suspect. The surviving victim and the suspect remain in hospital.

The motive for the attack is unclear, but Sgt Lewis said the suspect and the two victims do not appear to have been involved with each other outside of work.

Police were called to reports of a fight inside Vaughan Foods, with officers having been told a shooting had taken place.

Authorities say the suspect had recently been sacked at the plant.

Sgt Lewis said the man entered the plant and stabbed 54-year-old Colleen Hufford, severing her head, before he then started to stab 43-year-old Traci Johnson.

Vaughan Foods' owner and reserve county officer Mark Vaughan stopped the assault by shooting the suspect.

The suspect and Ms Johnson were taken to hospital, where they said to be in a stable condition.

Sgt Lewis said Moore police have asked the FBI to aid in the investigation and look into the suspect's background.