LOS ANGELES (AP) -- Los Angeles County jail officials separated black and Hispanic inmates, began transferring troublemakers out and brought in clergy to try to restore peace after a week of racially charged brawls they feared would continue to erupt through the weekend.

"It's got momentum," sheriff's Chief Marc Klugman, who oversees the nation's largest jail system, said Friday. "They're battle-hardened. They're angry."

Thousands of Hispanics and blacks clashed Feb. 4, and a black inmate was beaten to death, at the biggest jail at the Pitchess Detention Center, a 6,500-inmate complex outside the city limits. Brawls then broke out during the week at the two smaller jails at Pitchess. About 90 inmates in all have been injured.

Investigators said they do not know specifically what sparked the first melee. But Klugman said the fights that have broken out since then appear to be tit-for-tat retaliation by one side or the other.

Originally, investigators believed Hispanic gang leaders outside the jail ordered the first fight as retaliation for a street attack, but that proved untrue, Klugman said.

Klugman said about 80 percent of the inmates are affiliated with gangs in some way.

All of the fights appeared to be orchestrated by "shot-callers," or ringleaders, within the jails, officials said. Authorities said they were trying to identify them and move them out of their open dormitories to single-man cells at the county's downtown jail.

All 19,000 inmates in the Los Angeles County jail system will remain on lockdown through the weekend, meaning no visits or other privileges, Klugman said. It is hoped that will quell the violence, he said.

"We are taking away privileges. They don't like that. They want their commissary, they want their classes, they want their mail," he said. "That's going to start to wear on them."

On Thursday, sheriff's officials allowed 70 clergy members and about two dozen media representatives to talk with inmates. Many prisoners complained about being unable to shower or call home.

Many inmates really do not want to fight but risk a beating unless they stand up for their race, Klugman said.

The U.S. Supreme Court ruled last year that segregating prisoners by race is illegal except in extraordinary circumstances. The local chapter of the American Civil Liberties Union said the riot qualified.

Klugman said sheriff's officials view the segregation as both morally and tactically unsound in the long run and do not plan to continue it for more than two weeks. Separating inmates by race creates suspicions, and hands a victory to those inmates who want racial isolation, he said.

Pitchess has been the scene of more than 150 fights in the past 15 years, most often racially or gang motivated.