The day before state authorities announced plans to restrict inmate movement and revoke visits and other privileges, three inmates were killed in attacks at three different prisons.

California corrections officials say high-security prisons across the state are tightly restricting movement, calls and visits while they probe a surge in violence this year.

Los Angeles County and other state prisons are upgrading their security after a recent surge in violence against staff and inmates. The California Department of Corrections and Rehabilitation (CDCR) announced that it’s placing Level IV high-security sections within its facilities on a modified program,