Federal officials on [December 9] unsealed five criminal cases filed against 18 current and former Los Angeles County sheriff's deputies as part of an FBI investigation into allegations of civil rights abuses and corruption in the nation's largest jail system. Four grand jury indictments and a criminal complaint allege unjustified beatings of jail inmates and visitors at downtown Los Angeles jail facilities, unjustified detentions and a conspiracy to obstruct a federal investigation into misconduct at the Men's Central Jail. The FBI has been investigating allegations of excessive force and other misconduct at the county's jails since at least 2011. [An] official said the arrests were related to the abuse of individuals in the jail system and also allegations that sheriff's officials moved an FBI informant in the jails possibly to thwart their probe. Among those charged with conspiracy and obstruction of justice in the 18-page indictment are two lieutenants, one of whom oversaw the department's safe jails program and another who investigated allegations of local crimes committed by sheriff's personnel, two sergeants and three deputies. All seven are accused of trying to prevent the FBI from contacting or interviewing an inmate who was helping federal agents in a corruption and civil rights probe. In an attempt to find out more information about the investigation, one lieutenant and the two sergeants sought a court order to compel the FBI to provide documents, prosecutors said. When a state judge denied the proposed order, the two sergeants allegedly attempted to intimidate one of the lead FBI agents outside her house and falsely told her they were going to seek a warrant for her arrest, the indictment said.