In a letter sent to close family and friends, Jones claimed that a coach gave her a purported nutritional supplement that she later learned was a designer steroid, Washington Post reported late Thursday.
Jones has long denied doping, but the allegations intensified after she was linked in 2004 to the San Francisco-based Balco lab, which produced a liquid, oral steroid, known as THG or 'the clear'.
Since her connection to the Balco scandal, Jones has been the target of a United States Anti-Doping Agency investigation.
The International Olympics Committee has said it would consider stripping her of the three golds and two bronze medals from Sydney if it turned out she was not clean during the competition.
The Post reported on its website that a person who received the letter had read it over the telephone to a reporter. A second source with knowledge of Jones' legal circumstances, speaking on condition of anonymity, confirmed the facts of the letter.
The letter to Jones' loved ones comes ahead of her expected guilty plea Friday in a federal court in New York to two counts of lying to federal investigators, according to the text of the letter. The agents had interviewed her about both steroids and her personal finances.
In the letter, Jones said that 'the clear' was supplied to her by former coach Trevor Graham, who told her that it was flaxseed oil. She wrote that "red flags should have been raised" when Graham told her to keep the nutritional supplement a secret.
Jones tested positive in June 2006 for the banned performance-enhancer Erythropoietin (EPO), but the 'B' sample tested negative, clearing her of doping.
In November 2006, her one-time coach Trevor Graham was charged with making false statements to federal agents in connection with a doping probe. A string of Graham's athletes have tested positive for doping, and in August 2006, athletes trained by him were banned from competing in the final Golden League series stop in Berlin.
Jones' former boyfriend and ex-100 m world record holder, Tim Montgomery, had to serve a two-year doping ban based on evidence from the Balco case rather than a positive test.
In early 2006, Jones and Balco lab founder Victor Conte reached a settlement in her $25 million defamation lawsuit against the lab. Jones took Conte to court when he claimed he had given Jones a series of forbidden substances before and after the Sydney Games six years ago.