LITTLE ROCK — The director of Arkansas' prison system says a series of violent altercations at the state's maximum security prisons were due to correctional officers who failed to follow policy.

State prisons director Wendy Kelley told the Arkansas Democrat-Gazette that skipping required inmate searches and assigning less-experienced staff members to handle known troublemakers are among correctional officers' errors.

Kelley says crowding inside state prisons, maintaining a full staff and a volatile synthetic version of marijuana were not direct causes of the prison violence.

Since the summer, at least five guards and eight inmates have been hospitalized in instances of violence. One inmate died in August after a fight the month before.

In state prisons this year, staffers have recorded an average of 64 incidents a month of battery or threats of violence.