About 200 inmates fought in two dormitories at the North County Correctional Facility late Sunday, with 10 people suffering minor injuries that were treated at the jail, said Deputy Alba Yates of the Los Angeles County Sheriff's Department.
Investigators said it was not clear if Sunday's fighting was connected to Saturday's riot, which left 45-year-old inmate Wayne Robert Tiznor dead and more than 100 other inmates injured. None of the injuries were life-threatening, authorities said.
The lockdown remained in effect early Monday, and jail officials declined to say how long it might last.
Saturday's riot appeared to be fueled by racial tension and a feud between black and Hispanic gangs, investigators said.
Tiznor was jailed after being arrested Jan. 3 for failing to register as a sex offender, sheriff's officials said.
It was not clear whether Tiznor was singled out, said Steve Whitmore, a spokesman for the county's Sheriff's Department, which operate the jail system.
Black and Hispanic inmates at the facility were segregated after the fighting Saturday.
Authorities normally cannot segregate prisoners based on race or ethnicity because it is illegal, but legal advisers said it could be done in emergency situations, Sam Jones, chief custody officer of the county jail system said.
About 1,800 to 2,000 inmates were involved in Saturday's rioting, which lasted for 30 minutes to an hour, and about 200 inmates engaged in "serious fighting," said Deputy Steve Suzuki, another sheriff's spokesman.
The North County Correctional Facility is a maximum security complex comprised of five jails within one facility on a 34-acre site and houses about 4,000 inmates. It's about 40 miles northwest of downtown Los Angeles.
The county jail system, which is the largest jail system in the United States, on average has a daily population of about 21,000 inmates, according to the sheriff's department.