LOS ANGELES (AP) — Federal officials said 18 current and former Los Angeles County sheriff's deputies saw themselves as being "above the law" when they engaged in crimes that included beating inmates and jail visitors, falsifying reports, and trying to obstruct an FBI probe of the nation's largest jail system.

The investigation into corruption and civil rights abuses led to the arrests Monday of 16 of the 18 defendants. At least two no longer work for the department.

"These incidents did not take place in a vacuum. In fact, they demonstrated behavior that had become institutionalized," said U.S. Attorney Andre Birotte Jr. "The pattern of activity alleged in the obstruction of justice case shows how some members of the Sheriff's Department considered themselves to be above the law."

The 16 who were arrested appeared in court later Monday. Thirteen pleaded not guilty, and three did not enter pleas.

Flanked by some of his top command staff, Sheriff Lee Baca told reporters Monday he was troubled by the charges and called it a sad day for his department. He said the department would continue to cooperate with the FBI and that deputies who have been charged would be relieved of duty and have their pay suspended.

The Sheriff's Department oversees a jail system with more than 18,700 inmates and has a history of abuse allegations dating back to the 1970s.

Among allegations in a criminal complaint and four grand jury indictments unsealed Monday:

— Deputies unlawfully detained and used force on visitors to Men's Central Jail, included detaining and handcuffing the Austrian consul general in one instance, and in another, grabbing a man by the neck, forcing his head into a refrigerator, throwing him to the floor and pepper spraying his eyes.

— Deputies falsified reports to make arrests seem lawful or in one case, struck, kicked and pepper sprayed an inmate and made false reports to have the inmate charged with and prosecuted for assaulting deputies.

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— Deputies tried to thwart the investigation by unsuccessfully seeking a court order to get the FBI to provide documents and attempted to intimidate a lead FBI agent by falsely saying they were going to seek a warrant for her arrest.

Those charged with conspiracy and obstruction of justice include two lieutenants, one of whom oversaw the department's safe jails program and another who investigated allegations of crimes committed by sheriff's personnel.

They're accused along with two sergeants and three deputies with trying to prevent the FBI from contacting an informant by falsifying records to appear that he had been released when he had been moved to different cells under false names.

Birotte wouldn't say whether the lieutenant and two sergeants involved in the obstruction of justice probe were directed by their superiors. He declined to say if the alleged abuse was fostered by the department's top brass.

Others charged in the documents unsealed Monday are a deputy accused of possessing an assault weapon that was illegally modified, and three deputies — all brothers — accused of a $350,000 mortgage fraud scheme.

Baca, who has been sheriff since 1998, is facing his toughest race yet for re-election in 2014. Baca has acknowledged mistakes but also defended his department and distanced himself personally from allegations.

The sheriff said he has made improvements including creating a database to track inmate complaints. He has also hired a new head of custody and rearranged his command staff.

On Monday, Baca said he would accept the outcome of the FBI investigation, but strongly denied criticisms that abuse was rampant.

"You haven't seen me retire from the job," he said. "You haven't seen me blame somebody else besides me for whatever the challenges are."

The American Civil Liberties Union sued the Sheriff's Department in 2012 claiming the sheriff and his top commanders had condoned violence against inmates. The organization released a report documenting more than 70 cases of misconduct by deputies.

The Citizens' Commission on Jail Violence, in its 2012 report, said deputies used force against inmates even "when there was no threat at all," and referred to "a culture of aggression among some deputies in the jails."

A federal jury in October found Baca personally liable for $100,000 for failing to stop inmate abuse by deputies in Men's Central Jail in a case brought by a man who said he was severely beaten while awaiting trial.

In June, a two-year Justice Department investigation found deputies discriminated against blacks and Latinos by making unconstitutional stops, searches, seizures and using excessive force in the Antelope Valley.

Baca disputed the findings but said he had instituted reforms.

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Associated Press writer Robert Jablon contributed to this report.