Nearly 2,000 inmates rioted at a Southern California jail, throwing mattresses and banging heads against bunk beds, in an uproar that officials said stemmed from racial tensions. One inmate was killed.

County detention centers remain in a lockdown as interviews continue with hundreds of inmates and witnesses to the fighting.

More than 100 inmates were wounded and 20 were hospitalized with serious injuries from the nearly hour-long melee on Saturday, authorities said. Smaller fights broke out for at least four hours after the main brawling ended.

"The motivation appears to be racial tensions and a carry-over of a feud between black and Hispanic gangs," said Deputy Steve Suzuki, a sheriff's spokesman. Two days earlier, a Hispanic gang member was stabbed by a black gang member, he said.

Black and Hispanic inmates were being segregated, Sheriff Lee Baca said.

Authorities had information that a disturbance was imminent, but they didn't know the time or location, said Sam Jones, chief custody officer of the county jail system.

A 45-year-old black inmate was killed, Suzuki said. Sheriff's officials said the slain inmate was jailed after being arrested in early January for failing to register as a sex offender. It's not clear whether he was singled out.

Twenty-six wounded inmates were treated at the jail; the 20 hospitalized inmates did not have life threatening injuries. No jail employees were injured.

Suzuki says about 200 inmates did the most serious fighting and some threw heavy objects from the upper tier of the jail.

The North County Correctional Facility, about 40 miles northwest of downtown Los Angeles, is a maximum-security complex composed of five jails that together house about 4,000 inmates.

It is illegal to segregate inmates based on race or ethnicity, but legal advisers said it can be done in emergency situations, Jones said.

The jail has a history of race related riots. In 2000, a three-day riot at the Pitchess Detention Center in Castaic injured more than 80 inmates, leaving one in a coma. Attorneys representing 273 black inmates filed a civil rights lawsuit alleging the sheriff's department failed to disarm Hispanic inmates.

Several racially motivated brawls at Castaic jails in 1998 injured dozens of inmates. In 1996, 5,300 prisoners battled, leaving six guards and 123 inmates injured after the Mexican Mafia prison gang ordered an attack on blacks.