Dan Mihalopoulos of the Chicago Sun-Times followed up on an important story: Two years ago, the FBI raided the offices of Concept Schools, which runs charter schools in Illinois. They also raided one of its charters.

Chicago Public Schools’ officials were aware of the raid, and they exchanged emails about what to do. They decided to do nothing.

More than two years since the FBI raids brought the still-ongoing federal investigation involving Concept to light, the charter operator has continued to do business with contractors identified in court documents as allegedly having been involved in defrauding a U.S. Department of Education grant program, records obtained by the Chicago Sun-Times show.

The charter-management organization — which runs four taxpayer-funded charter schools in Chicago and dozens more across the Midwest — has paid more than $519,000 since the raids to companies federal authorities said were involved in the corruption probe and their subsidiaries, according to documents the newspaper obtained from individual Concept schools.

There has been no correspondence between CPS and Concept Schools — which gets millions of taxpayer dollars a year to operate its Chicago schools — regarding the federal probe, according to CPS and the charter operator.

A CPS spokeswoman declined to comment Friday, citing the ongoing investigation.

Three years ago, Mihalopolous investigated the number of trips to Turkey that Illinois legislators have taken, paid for by the Gulen organization. Michael Madigan, Speaker of the House. is the Gulenists’ best friend in Illinois.