The stabbing deaths of four inmates at a private prison in Cushing were the result of a turf war between two white prison gangs that also spilled over into other state prison facilities, the head of an Oklahoma prison workers group said Thursday.

Sean Wallace, the executive director of the Oklahoma Corrections Professionals, said Saturday's attacks at the Cimarron Correctional Center that left four inmates dead and four others injured resulted from a feud between the Irish Mob and the Universal Aryan Brotherhood.

"It's all about the Irish Mob trying to take over," Wallace told The Associated Press.

Wallace said he didn't know which gang the victims belonged to.

Neither the Department of Corrections nor the company that runs the Cushing prison — Tennessee-based Corrections Corporation of America — would confirm a motive for the stabbings, which remain under investigation.

As the violence erupted at the Cushing facility, large fights happened at the Jess Dunn Correctional Center in Taft and the William S. Key Correctional Center at Fort Supply and a stabbing occurred at the Oklahoma State Reformatory in Granite, Wallace said.

"They all happened on the same day," Wallace said. "That's why everyone feels like this was a coordinated deal."

Jail officials in both Tulsa and Oklahoma counties confirmed Wednesday they had been warned by the Oklahoma Department of Corrections about the potential for violence between the two gangs.

"After this incident, we just went back through and made sure these guys are separated," said Mark Opgrande, a spokesman for the Oklahoma County Sheriff's Office, who said about 20 identified gang members from each group were inside the agency's jail.

All Oklahoma prison facilities remained locked down Thursday, with inmates confined mostly to their cells and movement inside the facilities severely restricted, said Corrections spokeswoman Terri Watkins.

Watkins said previously that a preliminary investigation determined the stabbings in Cushing happened in quick succession as inmates at a medium-security wing of the prison were being let out of their cells into the exercise yard.

Both the Universal Aryan Brotherhood and Irish Mob are "white-only" prison gangs established in Oklahoma in the early 1990s, according to federal court records involving cases of methamphetamine distribution and other crimes. The Irish Mob is a criminal organization formed in the early 1990s in Tulsa, court records show.

The Universal Aryan Brotherhood, or UAB, was established in 1993 and is modeled after the Aryan Brotherhood, a California-based prison gang formed in the 1960s, according to a federal indictment involving multiple counts against several UAB members in Oklahoma. The UAB has a defined militaristic structure and is overseen and directed by a 12-member "main council," whose members are mostly housed at the Oklahoma State Penitentiary in McAlester, the indictment states.

Randy Lopez, who spent 20 years at the Oklahoma State Penitentiary before retiring in 2012, said he was surprised to learn the two gangs were at odds.

"Back when I was around them, the white prison gangs all got along," Lopez said. "If they're fighting, it's about business. With gangs, it's all about business."