Alameda County Sheriff officers are investigating. It happened about 8:50 a.m. sheriff's officials said on Twitter.
Detectives late this morning were still on the scene at the jail, which is located at 5325 Broder Blvd. and houses about 2,800 inmates.
No other information about the homicide was immediately available.
ACSO working a homicide inside Santa Rita Jail. About 0850 hours. Detectives on scene. Inmate suspected of killing cellmate. Pio Sgt. Kelly pic.twitter.com/J0Qx5HDT9C— Alameda Co. Sheriff (@ACSOSheriffs) October 11, 2016
The two inmates were in a locked cell when they got into a physical altercation when the one inmate was killed by his cell mate.
They were a maximum security area for inmates with behavior and mental health issues