A riot at a jail near Los Angeles has left one inmate dead and more than 100 injured before order was restored.
Twenty were seriously injured at the jail
Saturday's disturbance at Pitchess maximum-security prison involved 200 prisoners in "serious fighting" between black and Hispanic prisoners.
No guards were injured at the complex of five jails housing about 4,000, but 20 inmates were in serious condition.
The incident was sparked by the stabbing of a gang member at another jail two days ago, officials said.
The riot is said to have involved up to 2,000 of the prison's inmates.
The inmate killed was a 45-year-old black prisoner. Prisoners were not thought to have used weapons, but had thrown mattresses at each other and banged heads against bunk beds.
"The motivation appears to be racial tensions and a carry-over of a feud between black and Hispanic gangs," said a prison spokesman.
Paramedics treated wounded inmates outside the premises as wardens used teargas to quell the rioters.
Black and Hispanic inmates were segregated and a prison-wide lockdown was ordered, the spokesman told news agency Associated Press.
Keeping prisoners apart on racial grounds is illegal in the US, but can be done in emergencies.