Five-time Olympic medalist Marion Jones (search) injected herself in the leg with human growth hormone and was given other performance-enhancing drugs, the head of a Bay Area nutritional supplement laboratory under federal investigation told ABC News.

Jones' attorneys immediately denied that she ever used performance-enhancing drugs.

In an interview to be broadcast Friday night on "20/20," BALCO founder Victor Conte (search) said he started supplying Jones with performance-enhancing drugs in the weeks leading up to the 2000 Olympics, where Jones won five medals.

Conte said he gave her a substance called "the clear," which was later determined to be THG, EPO and insulin. He also showed her how to inject hGH into her leg.

"After I instructed her how to do it and dialed it up, she did the injection with me sitting right there next to her ... right in front of me," he told ABC.

Jones, who is under investigation for steroid use by the U.S. Anti-Doping Agency (search), has denied using any performance-enhancing drugs and passed a lie detector test arranged by her attorneys in June.

"Mr. Conte's statements have been wildly contradictory, while Marion Jones has steadfastly maintained her position throughout: She has never, ever used performance-enhancing drugs," said her attorney, Rich Nichols. "Mr. Conte is simply not credible. We challenge him to submit to the same lie detector procedure that Marion Jones passed."

Phone calls and e-mails to Conte's attorney, Robert Holley, weren't immediately returned.

Jones, who failed to win a medal at this year's Olympics, has never failed a drug test, but Conte said no accurate tests existed for the substances he gave her during the approximately 13 months he worked with her.

"I know that she was tested many, many times from the timeframe that I worked with her. ... And she obviously passed all those drug tests, including the ones at the Olympic Games," he said. "So as I told you earlier ... it's like taking candy from a baby."

Conte is one of four men indicted by the grand jury investigating the Bay Area Laboratory Co-Operative. Conte, BALCO (search) vice president James Valente, Barry Bonds' personal trainer Greg Anderson and track coach Remi Korchemny all have pleaded not guilty to the charges.

Conte also said he developed a plan to use drugs to help Tim Montgomery, the father of Jones' baby, break the world record in the 100 meters in 2002. Montgomery's attorney, Howard Jacobs, declined to comment on the charges.

Conte also admitted to giving steroids to Anderson, but did not know whether Anderson gave any of them to Bonds or other baseball players.