Prison officials describe scene inside as "chaos".
A riot at the California State Prison in Folsom left 11 inmates hospitalized Wednesday, including one who was shot by officers, officials said.
The disturbance in Folsom involved an about 60 inmates.
It broke out in a yard at the maximum-security facility shortly after 11 a.m.
In addition to the inmate who was shot, at least 10 were either stabbed or slashed during the incident.
Prison personnel shot six rounds.
Their conditions have not been released.
No other injuries have been reported.
It is at least the second known incident within a year at the prison commonly known as New Folsom, located 20 miles east of Sacramento.
The prison opened in 1986 next door to the much older Folsom State Prison, and holds about 2,800 inmates.
The same prison was the scene of a riot in May 2011, that sent six inmates to outside hospitals, two with serious injuries.