The Oklahoma medical examiner's office says four state prison inmates who were killed during a prison melee were stabbed to death.

Medical examiner's spokeswoman Amy Elliott said in an email Tuesday that 31-year-old Anthony Fulwilder, 26-year-old Michael Mayden, 23-year-old Kyle Tiffee and 29-year-old Christopher Tignor each died of stab wounds that are described as "multiple sharp force injuries" and that the deaths have been ruled homicides.

Elliott said full autopsy reports are not complete.

The four were stabbed and several other inmates were wounded during an attack or fight Saturday at the Cimarron Correctional Facility in Cushing, a community between the state's two largest cities, Oklahoma City and Tulsa. No prison staff were injured.

State Department of Corrections spokeswoman Terri Watkins said Tuesday that the incident is still under investigation.