Arizona police are questioning a 21-year-old Hawaii inmate in the death of his cellmate, a 23-year-old Hawaii man, last week at the Saguaro Correction Center.
Mahinauli Silva is expected to be charged with second-degree murder.
Eloy, Ariz., police said Silva admitted to strangling his cellmate, Clifford Medina, in their cell last Tuesday when the prison was in lockdown.
Police had no immediate information on a motive in the killing.
Officials had earlier declined to confirm how Medina was killed. Medina was found unresponsive in his cell Tuesday morning.
An emergency medical services team tried unsuccessfully to revive him, according to a brief statement from the Corrections Corp. of America, which operates Saguaro.