The Daily News on Friday reported the source of the $1 million loan, identified as "Person D" in the plea memo, was former Sallie Mae CEO Albert "Al" Lord.
Naylor's plea memo says $500,000 from the Sallie Mae Fund, the corporation's charitable arm, was misdirected by "Elected Official A" to help pay a $600,000 balance on the loan.
Another $100,000 to repay the loan came from a NASA grant.
The memo also said a Washington, D.C.-based political consultant - identified last week by the Daily News as Tom Lindenfeld - signed a promissory note to secure the $1 million loan. Lindenfeld worked on Fattah's unsuccessful bid for mayor in 2007.
Fattah, a 10-term Democrat, mentioned three times in yesterday's radio interview with host Solomon Jones that the federal investigation has been going on for more than seven years.
"They have spent a lot of time looking into it, and they looked at everything that I've touched and worked on," Fattah said of the FBI. "They've been very enthusiastic in their efforts."
Fattah repeatedly said he would never do anything to embarrass himself, his family or his constituents. He also complained about the interest from the news media now that there is a "cloud of suspicion" over him.
"They have no interest in any of the work I've done," Fattah said. "They never covered me."
While Fattah has not responded to requests for comment from the Daily News, he has been busy tweeting, including four pictures he tweeted of himself with President Obama in a 24-hour period Monday and yesterday.
Jones, who writes a weekly column for the Daily News, served as campaign spokesman for Fattah's 2007 run for mayor. He took over the WURD morning show yesterday.
On Twitter: @ChrisBrennanDN