LOS ANGELES (AP) – Two former top officials of the nation’s largest sheriff’s department have surrendered to the FBI in a widespread misconduct investigation stemming from abuse within the Los Angeles County jail system, officials said.

Former Undersheriff Paul Tanaka, the department’s second-in-command, and former Capt. William Carey turned themselves in early Thursday, according to U.S. attorney’s office spokesman Thom Mrozek.

Tanaka’s attorney, H. Dean Steward, said Tanaka plans to “aggressively defend” himself in court. Lawyers for Carey could not immediately be reached for comment.

Both men were expected to be arraigned later in the day on charges related to the investigation, Mrozek said.

Several sheriff’s employees have been convicted of federal crimes including beating inmates, obstructing justice, bribery and conspiracy. The convictions stem from a grand jury investigation that began in 2010 into allegations of abuse and corruption at the downtown Men’s Central Jail.

Prosecutors said the convicted sheriff’s employees tried to hide an FBI jail informant from his handlers for two weeks in 2011 by shifting him from cell to cell at various jails under different names and altering jail computer records. The FBI wanted the informant to testify to a grand jury.

The defense argued that the employees were following orders from higher-ups.

Tanaka retired from the sheriff’s department in 2013 and serves as mayor of the nearby city of Gardena. He ran to replace former Sheriff Lee Baca but lost by a wide margin to Jim McDonnell.

Baca resigned as the corruption scandal engulfed his department. He has not been named as a target in the investigation.