Guards at California prisons violated policy in nearly half the instances they used force on inmates during a six-month period in 2017, state investigators have concluded.

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In a 47-page report released this week, the California Office of Inspector General said prison staff failed to follow the rules in 48 percent of the 3,709 incidents reported at state adult and juvenile facilities during the period. In some cases, staff exacerbated the situation, prompting the need for force, the report said.

Along with the recorded incidents, the report reviewed 292 complaints of excessive or unnecessary force. Investigators found that guards did not adequately report an imminent threat in 68 of the incidents.

“While the number of such instances is relatively small in comparison to the totality of all use-of-force incidents in the period, the negative impact of any such incident involving unnecessary force can be quite significant in its potential to create tension between the inmate population and staff members, and in exposing the department to legal liability,” the report said.

California Department of Corrections and Rehabilitation spokeswoman Vicky Waters said the agency will hone its policies.

“Use of force in our institutions is not something we take lightly,” Waters said. “Every situation where use of force was employed is different, but it is done so to ensure the safety and security of staff, inmates and the public.”

Violations ranged from how the actual force was administered — baton hits, Tasers, pepper spray — to whether the incidents were adequately reported and investigated.

Investigators found that chemical agents accounted for 46 percent of total incidents, while physical strength and holds accounted for 33 percent. The remaining 21 percent were comprised of less-lethal projectiles, baton strikes, Tasers and firearms.

Five state prisons accounted for one third of the incidents: California State Prison, Corcoran; California State Prison, Sacramento; Kern Valley State Prison; California Correctional Institution in Tehachapi; and Salinas Valley State Prison.

Among the problems cited in the report:

In 68 incidents, officers’ own actions may have contributed to the need for force.

Few officials are complying with policy to video record interviews with complaining inmates. State investigators said the prisons department must find a way to improve compliance.

In many incidents, officers did not have safety or medical equipment available to respond to the emergency.

Eric Balaban, a senior staff member at the American Civil Liberties Union’s National Prison Project, said the best policies in the world won’t mean anything if they’re not enforced.

“If there’s not consequences for violating the policy, it won’t be followed,” Balaban said.

Investigators praised the prison system for its new tracking system for use-of-force incidents and its new training in de-escalation techniques.

The report also recommended stronger progressive discipline for staffers who repeatedly violate use-of-force policies, and that supervisors and managers be held accountable when their employees repeatedly violate those policies.

Investigators concluded corrective action was needed in two instances where inappropriate contact was made with an inmate. In one instance, an officer tapped an inmate on her shoulder with a flashlight in an attempt to get her attention, and in the other instance an officer tapped an inmate’s foot to get her attention.

In another incident, an inmate refused an officer’s orders to hand over a piece of paper that he received from another inmate. Even though he was told to relinquish the piece of paper, the inmate instead walked to his cell and attempted to flush the paper down the toilet.

The officer then administered pepper spray, which failed to stop the inmate from his attempt to flush the toilet, so the officer used physical force and a second burst of pepper spray. The warden determined there was no imminent threat to anyone’s safety or the security of the institution. He imposed formal discipline on the officer for his unnecessary use of force, the report said.