Despite being cleared of doping charges back in 2006, Armstrong, 38, is being investigated again for systematic doping.
In May, former teammate Floyd Landis (who admitted to doping himself and received a two-year ban from the sport) accused Armstrong and other cyclists of using performance-enhancing drugs. He claimed that the sport's biggest star also encouraged the practice among teammates.
Armstrong has dismissed Landis's claims, pointing to the cyclist's lack of credibility. Now, The New York Times reports that federal prosecutors have other cyclists to back the doping claims.
One former Armstrong teammate told the newspaper that he had spoken with investigators, detailed his own drug use and described the rampant cheating among the United States Postal Service team members, which Armstrong supported.
The cycling star's agent and manager did not respond to requests for comment. His lawyer, Bryan D. Daly, said any cyclists who accused Armstrong of doping were lying.
"They just want to incriminate Lance Armstrong and that's my concern," Daly said. "The bottom line is, if you take away the soap opera and look at the scientific evidence, there is nothing."
Sources close to the investigation said that more cyclists are expected to meet with the grand jury soon.