The FBI has begun an investigation of Corrections Corporation of America for the private prison company’s maintenance of Idaho’s largest prison. The company was found to have severely understaffed the violent prison dubbed “Gladiator School.”

Corrections Corporation of America (CCA) acknowledged last year that it had violated its $29 million contract with the state by understaffing the Idaho Correctional Center by thousands of hours. An external audit showed CCA fell short of full staffing at the prison by 26,000 hours in 2012 alone. CCA admitted after an AP investigation that employees falsified staffing reports, sometimes claiming guards worked for 48 straight hours.

Reversing his earlier position, Idaho Republican Governor C.L. “Butch” Otter finally ordered last month that Idaho State Police investigate CCA, though Democratic lawmakers requested the FBI take the case.

Idaho Department of Corrections spokesman Jeff Ray confirmed to AP on Friday that the FBI informed department director Brent Reinke on Thursday that the federal agency was investigating CCA.

Idaho State Police spokeswoman Teresa Baker said state police were no longer involved in a CCA probe.

"They [the FBI] have other cases that are tied to this one so it worked out better for them to handle it from here," Baker said.

AP could not reach CCA on Friday, though the news agency reported that CCA spokesman Steve Owen had previously vowed that the company would cooperate with any investigation into its practices.

The American Civil Liberties Union sued CCA on behalf of inmates of the correctional center in 2010, claiming the violence in the prison – due in part to understaffing – was so bad, it was called “Gladiator School.”

In 2012, a Boise, Idaho law firm also sued the prison on inmates’ behalf, claiming CCA’s money-saving understaffing at the Idaho Correctional Center led to gang control of the facility. The law firm said the lack of guard supervision led to an attack by one gang against another group, leaving some of them severely injured.

The audit, performed by forensic auditing firm KPMG, done for the Idaho Department of Corrections early this year found that CCA fell 26,000 hours short in 2012. CCA contested the results, as Owen has said the audit overstates the understaffing by over a third.