The FBI led a series of raids around the Bay Area Thursday morning, rounding up officers from Antioch and Pittsburg, in the culmination of an 18-month investigation into an alleged criminal network composed of law enforcement officers.

The raids came after a federal grand jury in San Francisco handed down an indictment that accuses current and former officers with a wide range of offenses, including criminal conspiracy. A U.S. District Judge has placed the indictment under a sealing order, but that is expected to change sometime Thursday.

The arrests mark the end of an investigation that started in early 2022, when a tipster informed the FBI and Contra Costa District Attorney that a group of East Contra Costa County cops were cheating on college tests to obtain education incentive pay bumps. The scope of the investigation later widened to include alleged violent crimes and drug trafficking, and precipitated a cascade of scandals that has transformed the Antioch Police Department into one of the most scrutinized law enforcement agencies in California.

After seizing several officers’ cellphones, investigators stumbled upon thousands of racist and homophobic text messages involving dozens of Antioch cops, shining a spotlight on racism within the department that many residents had been attempting to raise alarm bells over for years.

The scandal continues to rock the local criminal justice system. Prosecutors in federal and state court have dropped or dismissed dozens of cases that relied on the impugned officers; Contra Costa County has allocated millions for attorneys to review thousands more criminal files for potential dismissal.

In Antioch, a federal civil rights lawyer has filed a class action suit intended to force federal oversight on the police department. Meanwhile, California Attorney General Rob Bonta is attempting the same with a civil rights investigation into the city, based on use of force trends Bonta has called “disturbing,” and said caught his eye before the criminal probe became known.

Amid the fallout from the investigations, several high-ranking Antioch officers have retired, including the city’s police chief. A lieutenant who was already serving as an acting captain has been hired to serve as interim chief while the city finds a replacement.