An FBI sting investigating misconduct at Los Angeles County jails led to the arrest of 18 current and former sheriff’s deputies Monday on a range of charges, including conspiracy and obstruction, a federal prosecutor said.

“The five cases allege a wide scope of illegal conduct,” said André Birotte Jr., U.S. Attorney for the Central District of California. “This investigation started by focusing on misconduct in county jails, and we uncovered examples of civil rights violations that included excessive force and unlawful arrests.”

The FBI has been investigating reports of excessive force since 2011.

According to the Los Angeles Times, officials were being investigated for allegedly trying to hide an informant who was giving the FBI information after finding the cell phone he had been using to document officer offenses. They allegedly changed the name he had been held under several times and questioned him repeatedly about whether he would testify in an investigation. Sheriff’s officials say he wasn’t being hidden from the FBI but rather protected after he had been outed.