(CNN) Federal authorities are investigating former University of Southern California athletic director Pat Haden in connection with the national college admission scandal -- specifically about whether he was connected to a man heading the scheme, a source with knowledge of the investigation said.

Haden has not been charged in the scandal, in which wealthy parents were accused of bribing college coaches and test administrators to get their children into selective universities. But a few other former USC athletics employees were charged in the scam earlier this year.

Investigators are checking Haden's possible connections to Rick Singer , the scheme's mastermind, according to the source, who spoke to CNN on condition of anonymity.

Haden, in a statement delivered to CNN by his son-in-law Donnie Dixon, said he had met Singer but did not know anything about Singer's illegal activities.

"Like many people, I was introduced to Mr. Singer several years ago by a friend," Haden's statement reads. "I was unaware of his illegal activities and had no ongoing relationship with him whatsoever."

JUST WATCHED How the college admissions scandal unfolded Replay More Videos ... MUST WATCH How the college admissions scandal unfolded 04:00

Dixon told CNN: "I can also confirm that he (Haden) has not been contacted by federal authorities, and we have no reason to believe he is under any investigation."

Haden, a Rhodes Scholar , a lawyer, and a former quarterback at USC and in the NFL, was USC's athletic director from 2010 to 2016, when he retired . He also used to work as an analyst during football broadcasts for CBS and NBC.

USC said in March that it was conducting an internal investigation about the scandal, and was cooperating with the government's general investigation.

On Thursday, asked for comment about Haden, USC said: "While the university's own investigation led by the office of professionalism and ethics remains ongoing, USC will continue to cooperate fully with all law enforcement and regulatory investigations."

"Ensuring the integrity of the admissions process remains a top priority of university leadership," USC said.

The national scandal

A dozen coaches and test administrators were indicted on a racketeering conspiracy charge in March as part of the admissions scam. In addition, 33 parents were charged with conspiracy to commit fraud for allegedly participating in the scheme. Some of them have pleaded guilty , and others not guilty.

The scams allegedly involved parents paying Singer or his charity to facilitate their kids' entry to selective colleges, along at least one of two different routes

In one scheme, Singer paid others to arrange for cheating on students' standardized tests, prosecutors said.

In the other, authorities said, Singer would bribe college coaches, who then helped the prospective students gain admission to a university by falsely claiming the students were athletic recruits, though in reality the students never would play for the schools' teams.

College coaches do not explicitly decide who gets accepted into their university, but their recommendations to the admissions office carry weight.

Singer disguised bribe payments from clients as charitable contributions to the foundation. Rather than go to charity, much of that money was instead used to pay off coaches and athletics officials, federal prosecutors said.

Singer confessed to carrying out the scheme and pleaded guilty to charges of racketeering, money laundering conspiracy, conspiracy to defraud the United States and obstruction of justice.

Charges against former USC employees

Some USC athletics officials were caught up in the scandal, including former senior associate athletic director Donna Heinel, who was at the school during and after Haden's tenure.

Heinel was fired this year, after she was charged in the case. She has pleaded not guilty to a charge of conspiracy to commit racketeering.

Also charged were Ali Khosroshahin and Laura Janke , the former head coach and assistant coach, respectively, of USC's women's soccer team.

Janke was accused of working with Singer to create fake athletic profiles for students, both while she was at USC, and after she left her job.

In addition, prosecutors said Janke and Khosroshahin designated four students as recruits to the team to facilitate their entrance to USC, even though the students did not play competitive soccer. In exchange, Singer directed payments totaling about $350,000 to a private soccer club controlled by Janke and Khosroshahin, according to the indictment.