A homicide investigation is underway at the California Correctional Institution prison after the death of an inmate this week.

The California Department of Corrections and Rehabilitation says 26-year-old inmate Malik Campbell was found responsive in his cell Tuesday afternoon. Campbell was pronounced dead just over a half-hour later, officials say.

No weapon was found at the scene, CDCR says, but officials have classified the incident as a homicide investigation and have placed Campbell's cellmate, 29-year-old Donte Walker, in restricted housing.

Campbell's exact cause of death will be investigated by the Kern County Coroner. Prison officials say Campbell was serving a 26-year sentence for voluntary manslaughter out of San Diego County with a number of enhancements.

Walker is serving a four-year sentence out of Sacramento County for a second-strike second-degree robbery conviction. He was also convicted out of Placer County for criminal conspiracy.

California Correctional Institution is located in Tehachapi.