IONE, Calif. — Officials at a Northern California prison say they are investigating an inmate’s death as a possible homicide.

Mule Creek State Prison officials said Tuesday that 36-year-old Robert Dahl was found unresponsive in his cell Monday afternoon. He was later pronounced dead.

Officials say they consider Dahl’s cellmate, 46-year-old Todd Laverty, a suspect. Laverty is serving a life sentence for second-degree murder from Riverside County.

Dahl was serving a nearly 25-year sentence from Sacramento County for robbery and possessing a weapon as a repeat offender.

Mule Creek houses more than 4,000 inmates southeast of Sacramento.