Federal prosecutors will hear from at least two more witnesses that seven-time Tour de France winner Lance Armstrong used performance-enhancing drugs, reports the New York Times. Following accusations in May by former teammate Floyd Landis—himself banned from the sport for doping—Armstrong has faced increasing scrutiny from the Food and Drug Administration’s prosecutors. Tyler Hamilton, who is serving an eight-year ban for doping, was one of those recently subpoenaed by a grand jury looking into Armstrong’s case. The other cyclist, a former United States Postal Service teammate, has yet to be named. It’s unclear if either man has testified yet. Former teammates have good reason to avoid lying if they’re compelled to testify: sprinter Marion Jones received a six-month prison term after lying about her use of performance-enhancing drugs while testifying on behalf of her coach.