Raleigh, N.C. — The investigation into former Democratic presidential candidate John Edwards' affair and campaign finances is coming to a conclusion.

Sources told WRAL News on Tuesday that a major development would occur in the next two weeks. It could be an indictment or perhaps a plea deal. Sources said it's unlikely that prosecutors would walk away from the case.

The investigation appears to have zeroed in on money from a 100-year-old campaign supporter and attempts to hide Edwards' affair with a campaign staffer.

Former Edwards aide Andrew Young wrote in his tell-all book, "The Politician," that heiress Rachel "Bunny" Mellon gave Edwards a total of $700,000 as a gift. The so-called "Bunny money" helped fund the cover-up of Edwards' affair with video producer Rielle Hunter, who was pregnant with the former U.S. senator's child.

Political observers have said the money was a campaign contribution and should have been noted in Edwards' campaign finance reports.

There are also questions about millions of dollars from Mellon that went to The Alliance for a New America, a nonprofit that supported Edwards' candidacy. Money from the nonprofit was paid to a consultant agency that no longer exists.

WRAL News spoke with Edwards on Tuesday, but he declined to comment. In 2009, he released a statement through his attorney to say that he was confident no funds from his campaign were used improperly.

Young told WRAL News in a 2010 interview that Mellon was in the dark about how her money was being used.

He said Edwards' campaign finance chairman, wealthy Texas lawyer Fred Baron, used it to finance flights and pay rent on a California home for Hunter and Young's family during the period when Young pretended to be the father of Hunter's baby.

Baron died from cancer in 2008, but his widow appeared before the federal grand jury in Raleigh in January. Investigators have interviewed Mellon twice at her estate in Virginia, and some of her family members testified before the grand jury in December.

Although federal investigators in North Carolina have been in charge of the case, it has been under review by the Department of Justice in Washington, D.C., in recent months.

Sources said Edwards wouldn't be surprised if he's indicted.