Story highlights AbilityOne is under investigation after allegations of fraud

Federal investigators are specifically looking at accusations of bid rigging, favoritism

Officials at AbilityOne, SourceAmerica deny allegations of wrongdoing

(CNN) A federal grand jury is examining the nation's premier program that provides work for people who are severely disabled, after a series of CNN investigative reports detailing allegations of corruption and cronyism in what sources say could be the biggest fraud case ever in a U.S. government agency.

CNN has learned government investigators have issued grand jury subpoenas as they investigate the huge taxpayer-funded program, known as AbilityOne, and specifically its managing agency, SourceAmerica.

Along with bid rigging and corruption, grand jury investigators are looking into allegations the program is operating numerous contracts illegally, and not hiring enough disabled people to fill contracts as required by law, as CNN detailed in earlier reports.

The AbilityOne and SourceAmerica program dole out hundreds of multimillion-dollar contracts to scores of organizations. To get a contract, 75% of a company's work must be performed by the severely disabled, people who cannot get work elsewhere.

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