The AbilityOne program and the nonprofit agency that manages it, SourceAmerica, are being investigated by the Department of Justice and at least four separate inspectors general offices for allegations of illegal operations, financial fraud and mismanagement, corruption and "contract steering," sources tell CNN.
At Tuesday's rally, which celebrated the 25th anniversary of the Americans with Disabilities Act, some demonstrators held signs that read, "Shame on SourceAmerica," while others demanded more transparency in the AbilityOne program, which funnels about $2.3 billion of taxpayer money each year to organizations that employ people with severe disabilities.
Rep. Tammy Duckworth, D-Illinois, said she is "significantly concerned" by the investigations into the program.
"If there is any corruption in that program, I will absolutely be following it to make sure that we end that," said Duckworth, a veteran who lost her legs and partial use of her right arm in Iraq.
"Everyone deserves the opportunity to live as productive a life as they capably can, so we need to be sure to really protect their rights to work," she said.
Presidential candidate Rick Santorum, in a Facebook comment, urged Attorney General Loretta Lynch to get to the bottom of the allegations.
"As the father of a special needs little girl, I am sickened by these revelations. A nation is judged by how it treats the most vulnerable in society," Santorum wrote. "We are better than this."
Santorum called for the prosecution of anyone involved.
Sources tell CNN as many as half the companies contracting with SourceAmerica under the AbilityOne program may be violating the law by not employing enough severely disabled employees. Moreover, several lawsuits have been filed in recent years accusing AbilityOne and SourceAmerica decision-makers of steering contracts to benefit their own interests.
Kelly Buckland, the executive director of National Council on Independent Living, which organized the Tuesday rally, said the government should begin closely monitoring AbilityOne contractors to ensure they have a 75% severely disabled workforce, which the program's regulations require.
"They should change how they operate, so they actually guarantee that these jobs are going to people with disabilities, which they're not right now," Buckland said. "Someone needs to hold them accountable."
Buckland said the AbilityOne program functioning properly is important because job opportunities enable people with disabilities to provide for themselves, whereas disability benefits may trap individuals in cycles of poverty.
SourceAmerica has refuted the recent allegations
, saying no one who makes decisions on contract awards is employed by an organization seeking those contracts. AbilityOne refused to answer any specific questions, citing pending litigation, even though many of the questions did not involve litigation.